Today Microsoft released what is expected to be the final build of Windows Vista to leave Redmond before the final RTM code. 5744, like its predecessor, is built on the final RTM source code branch.
My only issue with RC1 (x64) was that it couldn't perform an upgrade over a pre-existing Windows XP x64 edition. That meant I'd have to spend hours reinstalling various pieces of software, a luxury of time that I can't afford right now.
I installed the 32 bit version on a separate partition on my plain vanilla Gateway AMD Turion notebook, but it would not recognize the sound card, so I gave up.
The main issue with this stuff, at least from the 64-bit standpoint, is driver compatibility. The same thing happened with Windows Server 2003 and Windows XP x64 - the manufacturers were slow to arrive at first base with their 64-bit drivers. We will see how it goes this time, eh?