Mmm I don't know. Self looks like yet another overdesigned thing at 100k+ lines of code that doesn't compile. After 3 mins on the site, I can't figure out the main thing it does.
Sure, the adaptive compilation is nice, and message sends and type inference, but how well do the UIs work?
It's sort of cool to see Urs Hölzle and Craig Chambers in the papers section.