Bear in mind, this is my first HD set, so my basis of comparison is a tube set. I hooked the Dish PVR to the Samsun via DVI->HDMI cable into HDMI2. My DVD player was with component cables at 480i (it's an old DVD player!)
1) SD looks much better than I was expecting from reports, and my limited experiance with a friend's crappy 800x600 projector. The extra resolution and/or wobulation do a good job of making things not crappy at least compared to SD on a smaller tube set.
2) HD looks great. There's just no other way to describe it. It took me a while to figure out the proper combinations of Dish PVR display settings vs Samsung settings to get all of the channels looking right. (leave dish in "4x3 mode" at 1080i output so that the dish doesn't try to do any scaling, and switch samsung between 16:9 and 4:3 depending on whether watching an HD channel or not.)
3) When I had set the dish PVR to 16:9 mode I was getting audio sync issues... i attribute that to the dish being bad at scaling and/or doing a double scaling introducing unneccessary lag and artifacts. When set as described above, it went away.
4) The DVD looked great. I'm not seeing a compelling arguement in getting a progressive scan player as the Samsung did a great job with scaling and displays. Matrix Revoltutions was very sharp and detailed.
5) Right now I've got my video set up someplace in between Standard and Movie and I like how it looks. A bit sharper than movie, good contrast, not so bright as standard for darker blacks and more vivid color contrast. Once I get my video calibration DVD back from a friend I'll see what the experts recommend and decide if I like that.
OVerall, I'm quite happy. Now I just need to find all of the proper remote codes for my JP3 remote to do everything.