Just came back after spending a few hours checking the two sets at John Lewis. Having read all the previous comments very quickly before I left, I was determined to see the difference in picture quality. If I couldn't see it, when everybody raves about it, then either my vision is impaired or there's something wrong with the display model, in which case I'm not making a perfectly informed decision. I'm not dogmatic, I want to be convinced before deciding.
So I went to the store. Again, the material they had playing on the sets were not helping (DVD on the Pio, SkyHD/SD/BD on different Pannys). Even more unfortunately, the two TVs were not side by side (but then again, as I said before, if the difference justifies almost double the price, then it should be visible even not side-by-side). I went back and forth paying close attention to details, colours, blacks, motion handling etc. I also connected my laptop to the two TVs. Unfortunately I could only connect it via VGA and neither TV accepted 1080p over VGA so I went for 720p for the Pio and 800x600 (!) for the Panny (the highest they allowed, maybe it has to do with my display drivers, but it doesn't matter anyway). I watched samples of a few movies, 720p and 480p. I could see ZERO difference. They both looked very good, but try as I might, I couldn't see
any superiority in the Pioneer.
Then I noticed the two bigger sets, the 60" Pioneer (6090) and the 58" Panasonic (58PZ700) that they had side by side

, playing SD material though!!!

Still, even with the SD material I was pleased to see for the first time that the Pioneer was indeed better. In fact
much better. I could see much better blacks, which produced better greyscale, and better colour tones overall. And then I went back to a Panasonic at another part of the room playing the same SD material and I could tell the difference in the black levels. So I was glad that my vision is not impaired, because until that time
everybody was raving about the vastly superior quality of the Pioneer, that after you see it, you do not want to watch any other TV, and I could not see it. My conclusion at this point is that the 5090 model at John Lewis Oxford Street is either badly calibrated/set up or is negatively affected by extremely bad positioning. Either way it does not look superior
at all to the Panasonic 50" plasma.
Also, regarding the glass reflection, I didn't notice any difference between the two sets. In fact if one of them was marginally better, that would be the Panasonic. Sadly, in this department they are both (as well as the vast majority of the new TVs) quite noticeably worse than my current TV, a 3yr old Syntax Olevia LCD, which has a great matte panel that does not reflect light at all.
So now I am assuming that the 5090 at the store is not properly set up and that the TV has in fact the same superiority in the black levels as the 6090 and it is
currently the best 50" TV in the world. And I can afford it. But I still find the 50pz80b a)
100% satisfactory for my needs and b)
way ahead in terms of value for money, and therefore it will most probably be my new TV.
In general, most goods and services are priced on a linear scale for logarithmic incremental benefits (or an exponential scale for linear incremental benefit). Somewhere along the spectrum, there is a point (different for everyone) where one feels comfortable paying for the increasing additional premium for a diminishing additional value. My mother is perfectly happy with a 28" CRT. I can't stand it. Most people I know think that my 37" is already big enough (or even too big) and that the picture is perfect. I see lots of room for improvement, hence the upgrade. So I can see why most people would not settle for anything less than the Pioneer, but I'm glad (or actually my bank a/c is glad) that I don't have the same need.
A question to Filo25: you said that "When watching anything on the PC I let the Pio handle the scaling rather than my 8800GT, and it does a great job there too. "
How do you have the TV do the scaling? Doesn't the PC constantly send 1080p signal to the TV?