One of my room mates bought a 50" samsung, model # is HL-S5087W, and its pretty good; it doesn't look very good with SD content and without adjustments I think the picture is a little harsh, way too much edge sharpening (you can see white artifacts around black lines etc). I made some adjustments to the picture and got it looking pretty good but overall I think there are better tvs out there.
when I get my own place next year I will be buying the mitsubishi WD-52631, in comparison to the samsung mentioned above, it is IMO, slightly better in all aspects (ie color quality, blacks, accurate sharpness and contrast etc), and only costs slightly more.