My wife recently updated her iPad2 to 5.0.1 and she likes it a lot. No problems so far. She was on 4.3.3 no JB.
I just did it last night. A couple of problems I had to deal with along the way:
* Went through a bunch of iTunes errors. First 1604, then 1602 and then 1601 (I think). Solved that by going to a different computer, reinstalling iTunes and restoring the iPad.
* Thankfully iTunes on my original computer recognized the iPad and restored all apps from my backup. Of course I lost all my books and music since I do not keep those in the iTunes library, but that's a small price to pay. Interestingly enough, last time I upgraded iOS, I also lost all .AVI files that I had in CineXPlayer; this time they showed up again.
* A couple of apps did not get synced back; seems I downloaded them when I was setting up a relative's iPad and got them under his Apple ID. Oh well.
* Since I was using FolderEnhancer before, naturally all my apps are completely screwed up and I get to sort and organize them for the fourth time in 12 months.
* Some in-app purchases seem to have been retained (like the 3D feature in CineXPlayer), but others have not (like the full game pack in the Atari app -- don't feel like downloading 100+ MB for a third and fourth time, so I guess I'll just wait until the next JB comes out to make sure my iPad is the way I want it before putting "the finishing touches" on it).
* Can someone tell me how to deactivate the GameCenter? I must have pressed a button or something when I set up teh iPad after the upgrade, and now I always get greeted with "Welcome back..." when I start a game that supports it. Call me paranoid, but I don't want my iPad to go online every time I want to five minutes of fun...
Other than that, subjectively iOS5 does seem to be faster/snappier than iOS4 before, but maybe I just carried a lot of baggage around because of the jailbreak. Still have not come around to testing or exploring all the new features, but I guess I still have a day or two before the next JB will come out (hopefully).
I do miss some of the customizations and enhancements, though...