I've gone with the WDTV series for my media needs - the earlier gens were very hackable but they've turned on codesigning in the latest WDTV Live Media hub range. They're not bad and play everything I throw at them (Sigmatek decoders, afaicr)
I'm still waiting for a device that handles XBMC well, is responsive, has an optical audio output and offers DTS pass-through -- apparently there's no such thing. Lack of support for DTS/DD 5.1 pass-through is the main problem; last time I checked Minix seemed to be close, but not there yet.
Since any new media player will be the replacement for my primary TV, it has to pass the wife and daughter test. :)