64 Bit Windows has finally come into its own and is the preferred platform versus 32 Bit in most situations. Unless you're using an old HP printer, then it becomes a potentially serious issue. I've found that most of the Vista 64 bit drivers work just fine in Windows 7.
If you're using a network printer it becomes a bit trickier - the Host Based Printing Systems don't print across the network, so they're right out even though they are often available in a 64 bit edition.
HP Universal Printing often works, and often does not. For example it wouldn't work with a network connected Color LaserJet 3600 Series. Instead I used the Vista driver from http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareIndex.jsp?lang=en&cc=us&prodNameId=501046&prodTypeId=18972&prodSeriesId=501044&swLang=8&taskId=135&swEnvOID=2100.