Upgraded to 4.1.1, and having a field day. So far it seems smoother, though I messed with the developer options right off the bat. An added animation scale gives a bit more control. Open things super fast, or super slow, all smoother.
A lot of it is stuff I won't figure out just yet. That whole "go online and this code" at the ATT site was sort stupid. The first screen I figured out it was a bit pointless, so I went through, made sure it wasn't something I could not reverse and promptly hit the <skip> button. Of course a quick note about what and why I was logging on would have been OK. Come to think of it, that entire process was like that. Glad I was at home to do the upgrade/update considering the size and amount of time to do it all.
It looks to me like there are a ton of things in there different. Some are subtle, some not so much. I've got several apps of the same sort of functions (flixter, IMDB in an "entertainment" folder. The folder has been replaced with an icon that seems to look like the love child of all the apps within.