I migrated back to W7 after trying XBMC way back after discovering that Vista was a useless, bloated, machine-slaying heap of lard.
I was pretty impressed with XBMC, even back then and it was only the desire to play games on the HTPC that made me switch back to Windows.
From what I've seen XBMC is extremely polished these days and probably the best "media centre" as long as media consumption is your only concern.
This is my signature. There are many like it, but this one is mine. However, my signature is neither my best friend, nor is it my life. I also have no desire to master it and my worth is not signature-dependent.