Just bought the PZ85 - recommended. Nice picture even on most SD channels and excellent picture through my upscaling Denon 1940 DVD. Was originally going for the PZ80 but saw the 85 in the shop and preferred it (also liked the design a little more). Got mine for £888 from PRC Direct (good service).
Was thinking of the W4500 (to the point of almost clicking on the 'Place Order' button) but then went to see it in the shop. Too stark for my liking, looking like the screen was covered in vaseline when watching SD, and my girlfriend said she couldn't watch it for more than 5 mins without getting a headache. Plasma on the other hand was much smoother, easier on the eye (but can still do vibrant if that's what you want). Found out that Plasma tends to be the better technology (at least for larger screens) but LCD is cheaper for the manufacturers to make as they produce it in warehouse size sheets which are then cut to size whereas each plasma screen is made as one.
So, that's the PZ85 - if you can go for the 800 then even better.
Arcam Solo Mini/B&W 685s/Panasonic PZ85 42"/Panasonic BD35 Blu-ray/Yamaha YSP-600 Soundbar/Bose Wave CD-Radio/Lars & Ivan BK21/Ipod Touch 32Gb/Ipod 5th Gen 60Gb/Grado SR60/Shure SE530/Wii