XP Pro 32 to Win 7 Ultimate RC 32. Running dual boot with two WD hard drives, one OS per drive. All of my work-related programs run only on XP Pro and IE6, and Win 7 came with IE8 which is completely incompatible with my work-related stuff, and there doesn't seem to be any way to roll IE back in Win 7.
I strongly resisted Vista, and I'm glad that I did. Win 7 seems quite nice so far, although trying to install SUPERAntiSpyware gets the IRQ_NOT_LESS_OR EQUAL BSOD, and ZoneAlarm tells me that I need to download SP1 to allow the installation (it must think I'm in an XP environment.)
Gigabyte GA-EP45-UP3P, E8500, 4GB OCZ 1066, EVGA 9800GTX+