On a (somewhat) related note, there's a nice new feature in IIS 7.0 that allows you to run both x86 and x64 worker processes side-by-side.  This wasn't possible with IIS 6/Windows Server 2003.  For details, check out rakkim's post on the subject.  This will be handy for me since one of the apps I maintain has a single web service that is dependent on a 32-bit COM component.  On IIS 6, that meant everything had to run as 32-bit, but with IIS 7, I can segregate that service into its own 32-bit app pool while leaving everything else in 64-bit goodness.