Our "only" disappointment thus far is its handling of SD material - much worse than on our 50" (Pan plasma).
I have a Pioneer DVR-57H running through a Pioneer 1121 to my 55ST30. I have tons of SD material on DVD and was really thinking about purchasing an Oppo 93 just in case it looked bad. To my utter surprise, the SD material looks and sounds amazing.... So good in fact that I'm not even considering Blu-Ray anymore.
When playing SD, which component is doing the Upconversion for you?
That is, what Resolution is being sent from the player to your receiver, and then what from the receiver to your ST?
Finally had a bit of play time, and after trying "all" permutations, discovered that By Far the best PQ was achieved by setting the Output Resolution of the blu-ray player to 480p - thus letting the ST do all of the heavy lifting.
Resulting PQ is still far short of blu-ray - and does not appear nearly as good as SD DVDs on our 50" (although am still guessing the the larger size of the 60" ST simply magnifies any flaws) - but at least it makes SD DVDs "watchable."
(Using the "Soft" Picture setting on the player also helps to reduce video noise.)