UPDATE: SQL Server 2008 RC0 download is available to the general public now:
Yes, I just read a post in Andrew Fryer blog about that: RC0 for SQL Server 2008 is out! But for now it is available only for MSDN and Technet subscribers and other select group of users. If you have an active subscription, you may want to give it a try while is still fresh. For those without subscription you can either get one, or be little more patient until RC0 is available to the general public.
BTW, did you notice the new SQL Server logo? I find it really nice!