I'd been using 'home theatre' pc's for years from mythtv to myhtpc to btv to showshifter to meedio.
And in my opinion the PC theatre softeare packages are now becoming way to complicated, and only bought my first xbox about 1 year ago for the sole reason to install xbmc and see how it was. I have revisited the PC HT front end several times, but always sitting there ready to go ( and use for everything) is my xbox with t3ch xbmc build running perfectly every time I press the button.
I now have 2, 1 downstairs (modchip) on projector/surround, and another upstairs (softmod) on TV & stereo.
(Just added the xbox upstairs that had myhtpc sw on it with tv tuner remote, but sometimes goes wonky when the pc comes out of standby), now xbox is instant on. and the kids can use my old laptop on the bench for playing pc games, instead of mixing the tvpc with media & pc style games.
Oh and the XBMC win32 port does actually work quite well (albiet a tad slow), and is OK for testing out your skinning skilz. :-)
May XBMC last for my lifetime...