I hit a couple of niggles during the upgrade, which wasn't really an upgrade as such (it was a fresh install).
I went from a not-really-mildly-broken-by-my-last-set-of-upgrading-shenanigans Windows XP SP2 installation to an XPx64 installation, on an AMD Athlon64-powered Asus A8N-SLI (an Nforce 4-based board), avec Nvidia 6600GT (just the one, at the moment).
I dropped in a new 200GB SATA drive, bought special for the occasion, disconnected the other two, and kicked off the setup.
About half an hour later, I was staring at the Welcome screen. First problem: no connectivity. Doops. But it booted in literally under 10 seconds. The little blue caterpillar didn't even get all the way across the first time. That's cool.
I lunged for my laptop, went to www.nvidia.com and grabbed both the latest nForce platform (6.25 BETA) and graphics (71.something WHQL Candidate) drivers, and stuck them on my girlfriend's USB memory stick (deleting a bunch of boring wedding photos to make space). To whichever deity is the owner of USB keyrings, my eternal thanks.
One installation of the platform drivers with-everything-ticked-full-steam-ahead-don't-worry-about-unsigned-drivers-and-damn-the-consequences-Reggie, the box wouldn't boot any more, it just stuck at a black screen.
I invoked Last Known Good after a reset, which undid everything I'd done wrong to that point. This time, I just installed the Ethernet drivers. This time, the machine could reboot.
I spend a bunch of time without sound, trying to work out whether I needed the weird (and slightly crackly in Brothers in Arms) AC97 codec I'd been using under XPSP2 (as supplied with the motherboard), or if I could use the Nvidia platform driver set - as it turns out, you can use the nForce platform drivers for audio on this board as well, they're not just for SoundStorm boards.
So, I didn't install the GART driver, the IDE driver, the hardware Firewall (I don't trust 'em), RAID or the SMBus driver, and the machine still boots. Network and Audio were all I needed from the nForce platform driver. Now, the caterpillar runs across twice, but it's still a 10 second boot. Ahh, sweet newness.
The video drivers went on next, and I'm happy to report they're working. Not that I have any games installed yet - baby steps. Baby steps.
Off to look for Cool'n'Quiet drivers, and other random bits and bobs, maybe try out a few games, put the .Net Framework 2.0 on it...