bill - 2:59 am on Jun 15, 2009 (gmt 0)
I've been running 64-bit Vista on my main workstation and performance wise it has been rock solid. The down side has been driver support. I have some old industrial printers and scanners that don't have 64 bit drivers and probably never will. I work around that by running a virtual machine and port jobs out through that. It's a kludge, but I like having the extra RAM option.
I gather the 64-bit version of Windows 7 doesn't have a mode to support 32-bit drivers.
Not that I've seen.
easy upgrade path
If you have a 64 bit processor and would like to add a silly amount of RAM then you can take advantage of the OS. Otherwise it may not make sense.