I recently took the plunge and bought a 46" HDTV. Prices have fallen up to 30% in just the last two months so it's a good time to buy. You'll get the best value by buying either a 46" LCD or a 50" plasma. Here's what I learned in the process...
I was focused on getting a set that supported 1080p (highest resolution) and I wanted an LCD over plasma for video gaming due to possible burn-in issues with plasma. It turns out that burn-in is not much of a problem with plasma these days so now I have a little regret over not evaluating plasma sets as a possibility. Also, 1080p might not be noticeable on sets that aren't extremely large (50" or higher).
As for the sets themselves, the best place to find reviews and information about them is at CNET Reviews and the AV Science Forum.
According to both of these sources, the best TV around right now is the Pioneer PDP-5070HD. It supposedly has great color and clarity but lacks 1080p support. I didn't realize how much of a difference color performance can make until I got my current set but I'm now convinced it's very important. The performance on my set is very good but it makes me wonder how much better it can get. You might want to wait until this Pioneer falls in price (currently $2800) or try to pick up a floor model. At least take a look at it in a store and see what you think. Here's the link to the set on Amazon:
http://www.amazon.com/ASIN/dp/B000G835DA
As for LCDs, it's pretty much between Sony, Samsung and Sharp. Here's the latest 46" sets:
Samsung LN-S4695D (this is the set I got)
Sony KDL-46XBR2
Sharp Aquos LC-46D62U
The Sharp has the best specs (contrast ratio, response time) but apparently there is a flaw in the set where irregular black bands occur in some images. I wouldn't be comfortable buying the Sharp online until they work out these issues. Sony is generally considered the best LCD but you have to pay for it. Samsung actually makes all of Sony's LCDs in their factories so you get a pretty similar product from Samsung for a lot less money.
Another option to consider is buying an older model since they are currently a lot cheaper. You can get last years Samsung LNS4692D 46" for $1900. The major drawback on this set is it doesn't support 1080p.
Anyway...that's pretty much it. Let me know if you have any questions.