Nice work boys and girls!
Just upgraded to rc1 and everything seems to be a-ok. I haven't clicked around much to see if all of the backend is working yet but the frontend looks good (seems a bit faster, too).
The flash uploader is working again! It quit on me in 2.6.x for some reason.
I'd like to see the codex updated to include all of the new template tags, function calls, etc. so I can update my themes.
WP 2.7 looks to be the cat's pajamas.