I've been running 64 bit on my home machine for over 5 years now. Some software is installed 64 bit, most as 32 bit. Minimal problems, most were VPN clients that didn't have 64-bit drivers (hello virtual machine).
I'd honestly recommend 64 bit OS without exception. SQL too, unless there's a really, really good reason not to.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability