Well, technically all HD material is 16:9. The pillarboxing to get the OAR of 4:3 is in the original transfer AFAIK, that's what keeps the Samsung or any other device from stretching something that isn't 1.78 (and why 4:3 HDTVs windowbox any 720p or 1080i 4:3 signal)...1280x720 and 1920x1080...
I've found it's a fingerprint issue. The Samsung is much less tolerant of dirty discs than any player I've come across. Clean the disc (COMPLETELY, including inner ring) and it will usually then accept the disc.
Space and bandwidth limitations. A title like "King Kong" or "Hulk" fill up the entire 30GB of the disc. Also, Dolby TrueHD requires an additional 5Mbps of overhead on a signal and the format is limited to 36Mbps total. That's why most early BDs were devoid of extras, the PCM tracks take...
One thing I don't like about the Samsung is that it doesn't seem to allow reverse freeze-frame stepping. Only foward (like on VCDs). I hope the Sony model changes this.