The S5100 has replaced the S590. Go with that one. And yah, I'd consider anything less than $150, cheap for a BD player.
i just picked up the s5100 last week based off of jack's recommendation of that player and doing some slight research on it after he pointed me in that direction. the oppo has more features, but they are features i would never use, so no way i could justify spending $360 more JUST to get an oppo.
i was using my ps3 just fine until it was pointed out to me recently that my version of the ps3 can't do both 3d and the hd audio track. that was basically the reason i bought a stand alone player over just using the ps3.
watched jurassic park 3d last night and it was awesome for sure. can't say the picture quality or anything is different than ps3, but it sure sounded great! and as jackburton also mentioned, it is nicer with bitstreaming that you can 100% know what audio source you are getting since the receiver will tell you exactly what it is. with my ps3, since i was using PCM it would just say "multi ch in" and i truly didn't know exactly what soundtrack i was getting.
another pro for me is that the s5100 runs MUCH cooler than the ps3. i have all my gear in a closet and i tested it out last night during jurassic park, which is over 2 hours long, and shut the closet while watching the movie. when i opened it after the closet was NOTICEABLY cooler than when watching a movie on ps3. i usually would keep the door open when watching movies to get more airflow in there, but my amp is really loud fan wise so it's nicer when i can close it. although, when watching a movie i can't hear that stuff anyways cause my system is cranking.