This is exciting to see! It's only a preview release, but cool nonetheless. The final 2.0.0 is expected to come out towards the end of February.
1.9.3-p286 was just released and i'm still on 1.9.3-p194 due to the enhancements that can be made to it that speed up startup time and add garbage collection.
Speaking of speed, it looks like there has been even more development in that arena, with some new patches that supposedly cut Rails boot time in half. More info on that.
Looks like i'll be building some rubies this weekend! Follow the title to see the release notes for the 2.0.0 preview.