Hi
Actually WD TV Live is one of the best MKV players around.But WD lacks certain features.DVD Navigation was one of them,but on huge public demand is introduced in latest ones ( Old ones can update firmwares to get the feature ).Playback of Apple media ( MP4 , M4V etc ) is alittle jittery but still watchable.
On the other hand the competitors like Iomega Director , Seagate Freeagent Theater plus ,Xtreamer has issues on 1080p MKV and HD AVI.
One thing that WD lacks is moviesheets .Otherwise it is avery popular player
Sanu