It seems like both build 5536 (buildt Aug 21) and 5552 has found its way into the internet.
None of them are RC1, but we are slowly getting closer to it.
Keep your eyes open, and see if _you_ can join the public beta test when RC1
get's released to the public.
http://www.winfuture.de/screenshots/-1966-1.html
for screenshots of 5536 (german).