As a regular here at Audiogon, I don't think there's too much we can tell you that you don't already know. And you certainly know that whatever anybody says, somebody else is going to totally disagree with it, so we'll end up being no help anyways.
For what it's worth, here's my opinion,... thanks for asking.
Technology: LCD
LCD has some advantages over plasma and plasma has some advantages over LCD. It seems to me that as time passes however, LCD is eroding plasma's advantages faster than plasma is eroding LCD's advantages. Until something else comes to market that kills them both (eg. SED or Sony's proprietary version of SED), I would take LCD (and I have). Plasma has brighter colours, faster response and better contrast. However, current generation LCD's are not so poor on these points that they are an issue any longer, at least in my view, ...no pun intended. On the other hand, LCD's have smaller pixels than plasmas. So you will get a sharper picture and better resolution on the new high definition formats, no matter which one it is, HD-DVD, Blu-Ray, or HD TV broadcasts. That's why you don't see small plasmas, by the way, like computer screens for example. The larger pixels on the smaller screen would be quite noticeable. It's just my opinion, but I find the "screen door effect" on plasmas caused by the larger pixels in thier grid pattern to be incredibly annoying. Once you see them, you always notice them. I even find it hard to look at CRTs now without seeing the pixel grid after having had an LCD for a couple of years.
Forget DLP. It's an interesting technology and Samsung do it well. However, it'll be gone soon. It's not as "flat" as plasmas and LCDs, so the consumer market doesn't want it. Ever seen a DLP in Wal-Mart? It's the eight track cassette of the TV world. We can make it, but nobody wants it. I will be flamed by the DLP owners for saying this. However, this is a normal psychological response as they attempt to reduce their cognitive dissonance from having bought one. However, they don't know where I live and can't find me anyway so I'm safe from them.
Resolution: 1080p
I don't know if anything is even broadcast in 1080p yet so it's of limited value at the moment on that point. However, it will be useful in taking advantage of newly emerging high resolution DVD formats. Since you plan on having your TV a long time, you may as well future proof the thing to the extent you are able to. Besides, any decent TV sold today will have 1080p anyways.
Features: multiple HDMI inputs and an audio out.
I have just one HDMI input on my TV. I wish I had at least two. It's good to have a couple for the same reason that you want an amp with more than one input. You are likely to have a couple of things you might want to plug into it: DVD player, DVD recorder, satellite box, cable box, game console. If the external devices you own don't have HDMI, they will soon. So when you upgrade them, you want to have the TV being able to take them in their full glory. More future proofing. Of course you could use some sort of switching box with multiple HDMI inputs. Yeah right. Just like you could do this for an amp with not enough inputs. Just get sufficient inputs to begin with and be done with it. Use the component outputs on the external devices if they don't presently have HDMI, and make sure the TV has enough component inputs. And you want audio out so you can possibly hook a pair of quality speakers and an amp to the TV if you wish. And being an audiophile, why wouldn't you want an an oppotuntity to spend more money?
High resolution format wars? Don't worry about it. Get a 1080p TV and it will take whatever. That's an issue for the external device choice, HD-DVD or Blu-Ray; it's not an issue for the TV.
Screen size: 55 to 60 inches.
Everybody who buys a TV wishes they bought a bigger one. But it has to be appropriate for the room and your viewing position. There are a variety of formulae and rules of thumb for screen size. One simple rule is that you should be sitting between two and five times the diagonal screen size away from the TV. So if you're twelve feet away, 55 to 60 inches would be good. You could go a little bigger, but the price jumps exponentially after 60 inches. I don't know if it's worth it.
Brand: Sony, Panasonic, Toshiba, Samsung.
Take your pick. Whatever looks good to you. I think the Sony and Panasonic are a touch better than the other two, but that's just my opinion. I wouldn't feel hard done by having any of them. I would avoid the budget brands. You get what you pay for. If you go with plasma, and you buy cheap, a year from now you'll be looking at a TV with lots of interesting pink and green lines on the screen.
I have a Sony, but I had a hard time justifying the price difference compared to the Panasonic. Sony still maintain the fantasy that their equipment is so much better that they can charge a premium for it. I'm increasingly sceptical.
Sony don't make plasma anymore. They believe the immediate future is LCD. Panasonic make plasma and LCD, although they believe that plasma is better. As noted, I'm in the LCD camp.
In a previous post, I believe you mentioned that you were thinking about putting the TV on the wall above a fireplace or some other inanimate object. That's fine so long as it is not too high relative to your viewing position. Otherwise it's like sitting in the front row of a movie theatre. Your neck can get a bit sore. And don't forget my previious advice that your chair should have beer glass holders.
