UI is just as smooth as it gets, both when dragging around and when launching apps.
It also solves one of my gripes with ICS, which was a sometimes quite noticeable lag on the keyboard when autocorrection was enabled. I installed Swift to fix that but now I'm back with the default keyboard and it's super smooth.
All in all JB is awesome, but there's one issue: Google Now results in Spanish aren't nearly as good as in English. Almost every single question you make gets a plain Google Search answer, which isn't bad but certainly not as good as it's supposed to be






