Bad Experience
FWIW, I tried (multiple times) to upgrade from 7232 (x64) to 7264 (x64) a while back and it failed. Each time it got 90% of the way through the process before Setup.exe crashed. Fortunately, the installation rolled back OK and I was able to continue using 7232 until I finally wiped it in favor of a clean install of 7600.16384. I later upgraded from that build to the RTM final, 7600.16385, and this time it went through without a hitch.
Note: I run a fairly complex software stack including SQL Server 2008 Developer, Visual Studio 2008, IIS 7 and lots of VMware VMs. This may or may not have contributed to my earlier failure with 7232, but the fact that I had a virtually identical configuration under 7600.16384, and it upgraded just fine to the next sub-build, makes me wonder if it wasn't something quirky with 7232. It was, after all, a bit of a "frankenbuild" - SoLoR assembled it from a leaked VHD which may have rendered it incapable of a smooth upgrade.
Regardless, I'd recommend a clean install of 7600.16385. Yes, it's a it of a PITA have to reinstall all of your applications. However, enough has changed between that build and these later RTM "escrow" builds that it's probably worth the hassle.
Anyway, just my $0.02 worth. Good luck!
RCK