The 320 is a high quality player that offers excellent BD performance and very good SD DVD upscaling. It is a slick design with a current featureset. Its weak points are limited to disappointingly slow load times and no gimmicky features (ie netflix streaming).
I am less so disappointed with this player, but moreso unimpressed. I see little reason why one would opt for this $400 player over a $275 51FD that offers nearly identical performance save DTS HD MA decoding and Profile 2.0, which appear to be tempered by lesser analogue audio decoding and smaller frame that seems to run warm.
In an ever competitive landscape, there are increasinly better and better players available. Differentiation in BD PQ at 1080P 24fps and AQ bitstreaming or decoded to LPCM is miniscule (minus tweaking). To me, it's largely a proposition of value and added gimmicky features like Netflix or Pandora streaming.
With a $400 street price, I think most folks looking for value, should opt for the 51FD. You will get identical load times (all be they painfully slow) and identical BD and SD DVD PQ (very good). I am rather impartial if not indifferent to BD Live, but do like the convenience of firmware upgrades via ethernet. In this regard, the 320 does offer some value, but frankly this feature set is becoming rapidly a "given" in BD players and is readily available in players flirting with $200 street values.
For those of us who are seeking high quality SD DVD upscaling, speedy load times, and tweak-full settings, my humblest of humble opinions is to get in line and spend the extra $100 for the oppo. $500 is a hell of a lot for a player whose featureset could become obsolete quickly in this rapidly developing media (3D, etc), but you really do get a heck of a lot more for the extra $100.
Once again, I am neither unhappy nor disappointed with this player; it is a great machine and offers very good upscaling and BD playback. That said, I do not think it excels in its value relative to the market or offers top notch quality.