I have a small SproutCore 1.6 project that I'll be moving to 2.0 in the coming weeks/months as it gets closer to release. I took an initial stab at it early in the alpha, and it is much, much, much more developer-friendly. I am very excited to work more with SproutCore 2.0.
I've done some work with the 2.0 beta. It's really easy to drop sproutcore into an embedded panel on an existing application now. I prefer the eventing conventions in sproutcore over the alternative – purely a matter of preference. I'm looking forward to the new UI kit, too.