I remember (maybe a year ago) people complaining about XMBC on RaspberryPI. Things like the menus being sluggish / having slight delays, maybe some issues with 1080p videos streaming over a network, etc. Have those been resolved?
I can play FullHD DTS movies (rips of my own blurays kept at best quality possible) over Wifi without any hickup at all. That's fine.
The UI sometimes could be faster/smoother, but it's good enough. Moving between menu items sometimes drops a frame or two. So that's in FullHD, maybe that's better at a lower resolution.
What i learned from my previous media center (a Boxee, so basically a commercial XBMC fork): To stream FullHD over Wifi use NFS, not SMB, it is a difference. Atleast in my setup movies wouldn't play without buffering every few seconds over SMB.
Edit: also, from my experience openelec seems to be a little bit faster. Maybe because it's not booting the whole Debian userspace but only a minimal Linux.
Also: You can overclock your rPi without losing warranty (within limits). I overclocked mine to the maximum (700MHz -> 1000MHz) and it's still running without any cooling! :)
