I went through pretty much the same thing early in December -- my old system running XP died (primarily power supply, plus whatever got fried in the process), new system is a Lenovo with Win 7 (dual-core,x64).
Only two real gripes with 7 -- as seems to have been their custom since they've been around, MS has renamed and moved many common functions without changing how they work, so there's a lot of hunting to find things. Plus (and I can't really blame MS for this) I've lost the use of many old-favorite 16-bit apps.
What's really interesting is the hardware housing ... it's got no floppy drive, and an external power supply, so even though it's technically a desktop it's about the size of a digital clock, quite a change from my old tower. Plus it has a removable base to permit it to stand on end (handy, since that puts the outlet vent on top), in which case the desk-footprint is only about 2x3 inches.