The Panasonic Viera TH50PX80U is a great TV and a great deal. I bought it after doing a lot of research. One key thing I learned was that 1080p is really not advisable for televisions under 56" - the experts say that you can't really tell the difference, and there's a big jump in price going from 720p to 1080p. While a 50" TV is big, it's just not big enough to make 1080p worthwhile. A 1080p 42" will cost you just as much as a 720p 50". You're much better off with the larger screen than with 1080p.
And the TH50PX80U is a beauty. It has great picture quality, and looks gorgeous too with its sleek, pure black finish. I got a solid black TV stand to place it on and it looks great. I have no regrets buying it - it was one of the best bang-for-the-buck purchases I've made.
I did a lot of price comparisons at sites like PriceGrabber, but surprisingly the best deal I found was at my local PC Richards (PC Richards is one of those stores that doesn't seem to be found on price comparison websites). I got the TV for $995.97+tax, and picked it up myself (with help from my family - it's a big box!). At the time it was the cheapest optoin by $100. Nowadays you can get it for $999 at a few places, including Newegg.
Panny makes some excellent plasma TVs, they are truly one of the top TV brands. In my experience they make better TVs than Samsung. Sony also makes good TVs, but in my opinion they're overpriced. The best TVs are made by Pioneer - they have the best rep in the business. However they also are quite expensive. If you want absolute high end stuff, go with Pioneer; but Samsung and Panasonic are better values, and I'd steer you in the direction of Panasonic.
Regardless of brand, bottom line is that you should go with a 720p unless you're getting a behemoth of a screen. You will be able to get a larger screen for the same price, and the larger screen will impact your TV watching enjoyment a helluva lot more than 1080p could.