Paul’s not kidding here. I’ve seen it. At work. The guy’s back on 2k3 x64 for now and recovering nicely. The x86 bits, as Paul mentions, work great (meaning they Just Work). Admittedly, x64 doesn’t get (nor deserve, IMHO) as much (testing/dogfooding/etc) coverage as x86, but hopefully the problems all boil down to a small number of core issues and the RTM bits will suck less for compat.
You think you’re tough? Then try running Windows Vista in x64 mode: It can make a grown man wail like a little girl whose brother just catapulted Barbie over the fence.
Quite quickly, it became obvious that x64 was going to be a nonstarter for me. So I wiped out the install and reinstalled the 32-bit version. And now, everything works. I’m so glad that only lasted half a day. Learn from my mistakes and just skip x64 unless you really know what you’re doing. Or maybe you just hate yourself.