yeah man. Ive tried xbox, 360, and PS3 as media centers. While the PS3 does playback more formats than the 360, you still miss out on WMV in HD on ps3. Likewise, you cant playback AVCHD on 360. The whole media center thing has been a disappointing affair on both consoles. Seems like we may never have an open ended media box like the old XBMC, on consoles anyways.
Been battling the whole thing for a while. Neither console supports exotic MKV containers, or exotic AVC encodes (bframes, etc). The best thing period is a mobile cpu in a ultra tiny form factor. You can also buy HDMI vid cards now, so HTPC's are more appealing than ever.
PS3 - RFoM, SSHD, WH
360 - H3