Okay, so I've both purchased scrolls and now got the XP Potion recipe and made some potions. I didn't want to use them for "grinding" but more to help rapidly level new characters through the basic skill point quests etc...
However, here are a few things people should know about trying to do this.
1) XP Potions/Scrolls have their timers continue to tick when in load screens. Considering the average load screen is now 3-4 minutes, that's a big chunk out of your potion time.
2) XP Potions/Scrolls have their timers start the immediate time you select your character from main menu and it begins loading. Again, 3-4 minutes wasted, and when you land in the city you left, it will probably do a double load (re-load) and that's another couple of minutes gone of the XP boost as you sit and watch the screen.
3) When questing, you often move in and out of different load screens to enter delves/dungeons/quest zones etc. This means more and more time of you XP boost is wasting away.
I did a test with a stop watch as to how much time out of a 50 minute MAXIMUM XP Potion boost was wasted with load screens... a WHOPPING 27 minutes on load screens from 50 minutes... only 23 minutes of XP boost ... less than 50% of the boost was ever useful.
What are Zenimax going to do about this? Probably nothing. So I'd suggest definitely do NOT waste your hard earned money on the scrolls from the Crown Store until they act on the load times, and maybe add something that pauses the timer tick - or adds some extra time to allow for that wastage.