I like the swamps in Hjaalmarch. I don't like swamps full of crocs, kotu gava, etc and both Shadowfen and Murkmire have mobs packed too close together.
One reason is how you get dismounted in places that don't seem deep. Yes, it is a swamp, but it is bad for game play, it's not fun.
Second, is how you don't see things very well. Everything is mossy green. Mobs are obscured by plants or partially submerged. Again, this is how a swamp should be, but since there is no extra reward for this added "difficulty", it's not fun.
Third, swamp areas are confusing, you get lost pretty quickly.
And finally, it's a matter of preference. I find the dark grey-green color theme a bit depressing.
[PC/EU] Tamriel Hero, Stormproof, Grand Master Crafter
Usually there's no clear path through them and they are filled with the most annoying enemies (flies, wamasu, stranglers, etc.). There's also the issue of traveling through them since if you are on a mount it's hard to tell how deep the water is and even the tiniest low spot will dismount you.
I for one love swamps and marshes! At least in games, don't want to actually be in them in real life. But in the safety of my home I love their aesthetics in games. The more fantastic and swampier the better!
Dismounting is not much of a bother to me, maybe because someone who mains a bosmer I'm used to it, swamp or not. But I've also gotten good at avoiding that or I just get right back up in the saddle.
What we really need is a good dark souls esque poison swamp. Something as perilous and deadly as Blighttown but not quite as annoying as the Consumed Kings Garden or the green-lit hell hole that is Black Gulch.