I just picked up the Pioneer Elite DV-48AV yesterday from a magnolia store (on an awesome employee price I might add). It rocks, the upscaling is the best I've seen, even compared to a PS3 that I am currently borrowing from a buddy. I don't think you could go wrong with this unit. When I went to pick up the player the Mag guy told me the new Denon's video upscaling is, and I quote, "so bad that being a disappointment would be an improvement". This is the reason I went with the Pio and it looks like it is definitely a wise investment so far.
Mike
PS. I had a thread asking the same question about the HD-DVD players, the overwhelmingly consistent response was that they are sluggish and very slow to respond which is the reason I went with the Pio