Sending this from Jelly Bean on my Nexus S.
I am satisfied with this update, thought not as satisfied as I had expected:
1 - Project butter works but don't expect iOS like performance at all. It is like UI transitions got almost 5% faster than ICS 4.0.4 , but the chokings caused by Dalvik GC still show themselves here and there. And it is not a 60fps experience when working with Google Maps or other heavy UI apps.
2 . Autospace is not automatically inserted after clicking on suggested words above the keyboard.
3- Google voice just works and it is really awesome!
4- Fonts apparently have a more precise rendering than ICS. Texts are now even more beautiful.
(Maybe I should reset factory my phone to get a better butterry smooth experience.)