Well, assuming that you are going to buy this HDTV sometime soon, here's some advice:
1080p is nice to have, but like it was previously said, won't see much difference in anything that's really under 47" (if I remember correctly) vs. 720p. Even if you were to consider 1080p, many tv's say they can do 1080p but they tend to upscale it (meaning, they aren't really "full" 1080p, which is 1920 x 1200 pixils, I know this cause my new macbook pro has full 1080p).
Also, these screens/charts is a MUST. Don't leave or even buy a tv without consulting these charts. I always use this and even use it to help customers who buy a new HDTV (work in electronics at a local store). It also will help you understanding my previous statement about 720p vs. 1080p and why you can't tell the difference in small tv's.
http://s3.amazonaws.com/carltonbale.com/resolution_chart.png
AND
http://s3.amazonaws.com/carltonbale.com/distance_chart.png
Great forum for HDTV talk and discussion is found here:
http://avsforum.com/
Top Brands (imo):
Samsung
Sharp
Sony
Phillips
Westinghouse
Vizio (great TVs but not the best nor the high-end tv sets, good for their very cheap and affordable prices).
Samsungs have far the best picture quality that I've seen next to sharp (Aquos are the nicest). Their contrast ratios are high which is nice to have in games and their gaming specific functions are good (especially the refresh rates). Samsung and Sharp are expensive but will last a good, long time and have alot of inputs for items.
Refresh rate in TVs are a must for gaming. The lower the refresh rate is then the less likely you are to get lag (from your end, sometimes you can't help because of "server lag"). You should look for TVs that are under 8ms in refresh rate.
Contrast ratio is a sticky topic, imo. Some believe that the higher the contrast ratio is then the better the TV must be. Granted it is nice but some manufacturers overrate their products. Contrast ratio is the ratio of white to black in color. Say a Samsung contrast ratio says 3000:1, it is saying that white is 3000 times brighter than black. It also depends on the lighting in your room in which this will make a difference. Kinda like pc users who choose glossy vs. matte in screens. All depends on what you want to get from your TV and if you can deal with black not being as dark as say a $1500 tv.
Another thing to note is that there is a HUGE difference between the dynamic contrast ratio and the true contrast ratio. Samsung loves to say that their TVs are 3000:1 or 5000:1 or even 8000:1 contrast ratio but in reality thats not even close to the true contrast ratio. I want to say that they are about half of the dynamic contrast ratio but its actually a little above (meaning, its about 2000:1, 3500:1, 6500:1 respectfully). Don't quote me on this but there is a difference though in quoted and true contrast ratio. Don't be fooled.
That's all that I can think of at the moment. Hopefully this helps you. Good luck! I hope you find a great TV.
*Edited to say that it is not quoted contrast ratio, it's referred to as dynamic contrast ratio*