In my instance I do not think the burner plays back as well as a regular player. I have the DMR E80 panasonic which overall is great. But playing back DVD's whether commercial or recorded by me, always look better on my CP-72 - cousin to the RP-82. I have tried all the possible choices for playback but the E80 to my eyes does not quite match the playback of the CP-72. But, you would not by any means call it a bad picture - it is quite good actually. Just not quite the CP-72.
Playback with a Philips DVDR-985 is one of the best I'v seen with its built in fl2200 Faroujdia chip set, has very stable output, Maybe implemented better then other comparable units containing the same chip set.
If you're looking for best picture quality in the playback of DVDs, I think a stand alone player would be your best bet. But the convenience of having a recorder/player in one box is hard to ignore. My Sony RDR-GX7 recorder is a fine playback machine, but picture quality is a bit on the soft side when compared to my Sony NS999ES Player. Also ease of use is better with the player. But again, for what you get, you can't go wrong with a good DVD recorder.