I am still not aware of ANY brick and mortars that have the 52", even though some here claim some BBuys have them.
I did indeed get my 52" XBR4 from BB this weekend. Not on the floor or website, but certainly in the store inventory computer. Of the two BBs in my area (Eastern WI), only one had one 52" in stock.
For my set, minor clouding is noticed only when a blank screen is up, never during letterboxed movies or other times. The black level is good for LCD, but not perfect, yet. I still have more tweaking to do, but am overall very pleased. This set blows away my old 57" Hitachi RPTV. Everything's so damned crisp!
Letterbox bars aren't completely black, but not distracting. I'm currently running the PS3 via HDMI on standard mode, cool color, blacklight 5, brightness 45 (or 50, can't remember right now), contrast 80, with CE on medium, black enhancement on low, and power saving on low. I tried upping the power saving to high and although the black level improved, the picture just lost the 'pop' that I love so much. Lowering brightness or contrast took away too much detail.
And for those wondering, yes, the TV still lights up a room with no image present on screen, though only minorly.