Meh.

I performed a clean installation of Android 4.1.1 (Jelly Bean) on my Nexus S about three days ago, and it's definitely slicker... Battery life seems a little worse so far (10~12 hours of average use per charge), Google's weather app only works when location services are turned-on, and Google Now doesn't seem to do much for me - specifically, the public transit card doesn't seem to work; perhaps my city isn't supported; perhaps I'll get around to looking into that. Otherwise, I've had the phone start-up in safe mode once (probably my fault), and Swype has been changed from being my default keyboard. So yeah, Android 4.x has been a very pretty and mostly functional, albeit slightly buggy and more power-hungry-than-is-convenient experience.