I really enjoy this player....it has become my primary DAP.  The SQ of this player is extremely good, especially at the price point of ~US $130.  I wanted a very clean source to play through my tube amp and am very impressed.  For my purposes, the limited video capabilities and somewhat kludgey interface are not issues.  The build quality is relatively high, it plays FLAC and AAC (as well as others), has a true line out, and its architecture has been implemented well.  It also has plenty of power for even demanding headphones. 
 
I would recommend this player to anyone wanting very HQ audio without carrying a separate DAC/AMP.  If you are looking for more of a video player, go with the cowon.  The touch screen is decent and has excellent resolution, but its not as sensitive as an ipod, droid x, or my P2. Honestly, the interface (v2.30 on my T51) is about as good as my Samsung P2 before I flash ugraded it....actually less buggy.  Battery life is short compared to other players (6 to 8 hours) due to the abundance of chips in this thing...also the reason it weighes 3x more than my P2.  The T51 also only has a few settings/options that are confiigurable compared to other more mainstream players.  Navigating larger music collections via the interface is also a bit cumbersome, but tolerable.  
 
The text-to-speech eBook reader is a nice addition and works surprisingly well despite having only one english speaking TTS engine.  One gripe is that it reads only txt and not PDF's.