Not convinced by SproutCore
I have been using various frameworks in the past year or so and have quite some experience in it.
I don't think that SproutCore deserved all the credits it's currently getting. The only real application so far deployed on some decent scale is Apple Web Gallery (or rather .Mac), and honestly performance are lacking badly.
It's remind me a lot almost Microsoft here with how much vaporware stuff is being written when no one for sure has seen a final working app. I think that July 11 is going to show what I suspect : beautiful user interface (classic Apple) but poor performance.
Here is what I suggest when everything is available : let's check browser memory footprint and overall application response time for loading and using it... I think that until we have something to see and use, it's a lot of wasted bandwidth to claim that SproutCore is solving every problem of the web !
As mentioned in an earlier post, Cappuccino is way more oriented toward Cocoa than SproutCore !
SproutCore force you to use Ruby for your development : this is a no go for many folks.