Windows 8 is actually incredible. As I said, you can completely bypass the new interface.
Since XP 64-bit drivers weren't that common for many components, AND your computer had Vista on it you may have difficulties with some drivers. Conversely, Windows 8.1 64-bit is so new it likely has most or all of the drivers you need right on the Install disc.
On my dad's Vista laptop I did a fresh install of Windows 8, and the ONLY driver it didn't install was for the card reader (I tried the Vista driver from the laptop support site and it worked). I did update the NVidia graphics driver to a newer one as per normal. His laptop booted up in about 30 seconds on the 5400RPM hard drive (six-year old laptop) and has been rock solid and smooth even with only 2GB of System RAM.
I then got Start8 for $5 to bring back the Start Menu, disable the Charms Bar and then I changed the settings to boot directly to the desktop so the interface is basically EXACTLY like Windows 7's.
Suit yourself of course, but unless you have programs that won't run on Windows 8.1 64-bit (even after applying XP SP3 compatibility mode for the program) I see no point in NOT getting Windows 8 as it's just far better.
*You can also look up the COMPATIBILITY of your software:
http://www.microsoft.com/en-ca/windows/compatibility/CompatCenter/Home?Language=en-CA