This version is based on build 639.11. The public beta version of Exchange 2010 was based on build 482.20, so as you can imagine a lot has happened since then.
Via my involvement in the Exchange 2010 TAP and RDP (since Q2 2008), I’ve had the pleasure of testing each and every version released since then (both in production and in my test environment) and I must say I’m very impressed with this Exchange Server version. The Exchange team have really done some incredible work!
You should never ever install Exchange 2010 beta/RC software in production unless you’re participating in the Exchange 2010 TAP or RDP. If you screw up you’re on your own. Microsoft Product Support will net help/assist.