Okay - my 50PV350T was delivered on Friday.
I'll give my first impressions, all wrapped up in fact I got it for just under £500 from Amazon. I don't think I'll say anything new, but it might add a little weight to someones purchasing decision
Picture quality - top notch as far as I can tell. I'm sure spending another £1000 would improve it, but I'm not going to do that so it's irrelevant really. Image retention - the old stories about IR and screen burn scared me off from plasmas a little, but now I have one, I don't see it as much of an issue. There is some slight IR - especially if I'm looking at the Windows 7 display from my HTPC, but it disappears very quickly once it has some movement across it. I am being gentle with the brightness, but I don't think i'd want the screen much brighter anyhow. I am going to let it settle for the few hundred hours people talk about on here, and then "calibrate" by eye properly. I've seen the little green dots some people have talked about, but only when sitting about 15" from the screen, not a normal viewing position!
Only two HDMI ports. I could see this being a big problem for some people. Previously I'd have had the opinion that people with a 50" screen would always have a 'proper' AV receiver set up, but at the price these TV's are now, I don't think that can be assumed as a given.
Sound - I only know this as I flicked through the Freeview HD bits when I was setting it up, it's Okay. Certainly bearable. What do people want from two little speakers stuffed into a flat box?
Menu's and UI - Again, I do nearly everything via my AV receiver, so this is almost redundant. However, I actually like the menu's quite a bit, they're clear and things are fairly obviously labeled.
My main complaint about the TV is the lack of a proper printed manual. The full manual comes on a CD-ROM. I know this is the way many things are going, but I still find it irritating! In the end I downloaded it from the LG website to Dropbox, and then sent the PDF to iBooks on my iPad. A slight abuse of technology in order to replace something as simple as a bit of printed paper.