Just thought I would put down all my thoughts about the game into one comprehensive post. Note that these are my personal opinions, but feel free to speak up with your own views on anything. Also, it's a wall of text.
Questing
One of the most interesting and well-done features of the game, the quests in ESO really surprised me with their depth and quality. It is extraordinarily difficult to make quests feel different in an mmo but it's pulled off very well here, up until a point at least. The one downfall is the bugs that really put a dampener on whatever you're doing when they crop up. With the dozens of fixes in the latest patches, however, you can tell that the devs consider this a high priority and that questing is something they want to see flourish. While the diversity of quest types and objectives was high, and there were some genuinely funny dialogs, some patterns did start to emerge at the later levels, (and most especially at veteran levels, although I'll come to that later) and soon I was skipping past the side quests to get to the main story lines. Overall, I'd say they did a fantastic job here, and I haven't seen better in any mmo.
Solo Dungeons
During questing you come across solo dungeons often enough, and if you were unfortunate enough to do it around early access, they were infested with bots and boss campers. Now, that's a lot less of a problem thankfully, and when everything goes right and you actually solo the dungeon then it's a pretty cool experience. The progression is always very linear and the boss is usually very predictable but there is usually some decent loot at the end, an achievement, and a skyshard so the sense of accomplishment is all there I think. Unfortunately, most of the dungeons are made in exactly the same way: one big square. You go around in a circle then exit through the locked door after killing the boss and grabbing the shard. A little more variety in those environments would have gone a long way I think. Also, when there are too many people in the instance it is far too easy and just becomes a run to go get your loot. Having solo dungeons be instanced to a max of a few people might be a good fix for that.
Group Dungeons
These dungeons are interesting and can be very fun or extremely annoying. The biggest problem they have is attracting the right kind of people. You either have too few people who want to do the quest and complete the dungeon or too many people who want to farm the mobs. Getting a group, or just tagging along with people, is really what the challenge is in these dungeons and I think there should be some way to encourage or enable grouping when you enter a group dungeon. Perhaps something as simple as an incentive to group, like a small xp or loot bonus for the number of people in your group, would help with this. Overall though, I like group dungeons, they have variety, challenge, and can be very rewarding when everything and everyone comes together.
Dungeons / Veteran Dungeons
The four man dungeons were extraordinarily buggy the first time I went through so my opinion on these is a bit biased. Even on the veteran dungeons, there are just too many 'cheese' techniques that groups use as a matter of course. In vet BC, I just remember thinking that half the bosses were easy and the other half were glitchy. When playing the dungeons the way they're meant to be played though, in a good group, it can be a great experience. I'd say the dungeons aren't bad, but they could use some work.
Veteran Levels
So veteran levels...nobody really likes them I guess. (Spoiler Alert) When I killed Molag Bal I felt like a total bad*** then I get a pat on the back and Cadwell says "Hey man, touch this crystal thingy to be a noob again!". Well, no wonder nobody likes veteran levels, you have to start all over again. It doesn't feel epic or end-game, like it should when you finish the main storyline quests. On top of that, having to do the basic errand-running quests as your new faction's (and former enemy's) peon makes you feel a sense of deja vu as the quests start to repeat a bit and the voice actors start to re-appear. It has a sense of "been there, done that" to it, and on top of that it feels like it takes forever because of the amount of xp needed. I know the devs are looking at changing this and that's a good thing, because it badly needs it.
Trials
Released with Craglorn as the end-game raiding content, these were surprising hard and are clearly designed with hardcore players in mind. A poorly organized group will no doubt wipe over and over and that leads me to the first problem. Since each group only gets a certain number of "souls" (revives) they have to leave the instance and disband then reform the group and re-enter before each try. That seems stupid to me. How about the group leader presses "R" in the group window to reset the trial? Other than that, the trials themselves are alright I suppose. I must admit, I am not a fan of beating on the same bosses over and over, so I am not the most unbiased reviewer in this category. I think the difficulty level is alright, but there's some bugs to fix and definitely some balancing changes in the classes to make.
Economy
Any successful mmo has to have an active trade economy. With ESO's unique move to guild stores the player to player trade is a lot higher than in other games I've played. When the game first came out the COD tax was incredibly high, prohibitively so, but in a recent-ish patch they lowered it to a much more reasonable amount and I think that has helped trade considerably. From what I've seen in my server there seems to be a veteran trade hub which is a good sign, since commerce gathering in one spot is good for everyone. Prices seem to have stabilized a bit, although motifs have been all over the place, and don't look like they'll be stabilizing for reasons I won't get into. The DC farm probably needs a fix or at least a nerf, but overall I'd say the economy is fairly healthy, which is a good sign.
Crafting
The crafting system in ESO is unique in that you have crafting skills that you can spend your skill points on instead of class skills. This is an interesting dynamic and I really like what that brings to the system. As for the professions, provisioning is too easy to level, has too many ingredients, the drinks should go on top of the food, and the veteran zones need their loot tables fixed. Alchemy is the next easiest to level, and a little too easy, the passives snake blood and medicinal use are broken, and the ingredients aren't balanced in terms of usage unless poisons are implemented. Enchanting takes way too long to level and Aspect Extraction is mostly useless. The big three are well done, although woodworking could use some more items.
Visuals/VFX
For the most part, I really like the graphical style of ESO. I am blown away by the quality of some of the environments and the detail for an mmo is just astounding for someone whose first mmo was Everquest on Playstation. Some of the effects for spells look pretty awesome and the only complaints I can think of are winged twilights in banks and that some don't like magelight. There do seem to be some issues with physics volumes (it looks like) having precedence in LOD calculations but other than that, I think ESO has been on the ball in the graphics department.
Writing
There is an absolutely incredible amount of lore written down in lorebooks and journals and notes and scraps of paper all over the damn place. Novels are there to be read and the quality of it is insanely good. One of the perks of the mage's guild is Eidetic Memory which lets you re-read everything you've ever read and I think that might be the best perk you can get. Between the random mail from a hireling that makes you laugh to the priceless comment from Cadwell in Oblivion, you'd be hard-pressed to find better writing.
Audio
The ambient sounds and musical scoring of ESO are great, and definitely do the elder scrolls name justice here. It's rare to find an mmo where you can actually listen to the music for hours without going nuts. Also, the voice acting is top-notch in my book. Some of the characters in the story lines were downright awesome and it was in large part due to the voices. There are a few abilities that could use a change (Harness Magicka, I'm looking at you) but otherwise, the sound is very good.
Cyrodiil
I saved this one for last because I feel rather strongly about it. There is so much potential in the open world experience that Cyrodiil offers that I am amazed it isn't a bigger part of the game. And that's the real problem, it doesn't feel like a big part of the game. There are a host of bugs that have been plaguing Cyrodiil but no fixes and not much concern shown for it so far. Bugged forward camps, bugged siege weapons, bugged repair kits, bugged doors, bugged map, bugged compass, bugged... well you get the idea. The thing is, pvp in Cyrodiil can be extremely fun when everything is working right. The basics are there, but the list of bugs is not short and as a whole, not minor. There are also some severe issues with farming (emperor, scroll, oil) and a disturbing tendency for tight-knit aoe zerging. These issues are leading to a particular play-style dominating all others, which never results in an attractive pvp environment. Cyrodiil is one of the two pillars of end-game content and in order to keep and promote a balanced end-game population you need to have both in working order. Right now, Cyrodiil is not in working order.
Well, that's my review of the game. If it was too long, and you didn't read it, post something witty and nonsensical below.