I went through a few LCD's in my home before I finally got what I wanted. I bought an Insignia from BB...it was actually a really nice set, but it had an electrical problem so I returned it within the 30 day no hassle return period and swapped it out wiht a Toshiba Regza. Another nice set whose backlight overheated on me and cracked the LCD panel. Returned that after some arguing wiht the BB manager and got a Panasonic 50" plasma set. Hung it on the wall in the living room and its just fantastic to look at. I have a wall of windows on the West side of the room (see my avatar, thats my house) and there is zero problem watching tv even on the brightest days...the Panasonic plasmas have an anti-glare coating that many other manufacturers do not seem to use for reasons unknown to me since glare and power consumption are the two biggest hits I see against plasmas.
While I was in the middle of a two week argument with BB over the Toshiba my wife and I went out and bought a Samsung 40" LCD, which is now in the upstairs bedroom. Another great set.
On top of this, I have been buying large format displays as the IT Manager for a bank...I have about 2 dozen 40"+ displays out there and they run the gamut of brands...Viewsonic, LG, Sony, Panasonic, Samsung. I won't buy anything bu panasonics and Samsungs anymore...the others have never measured up in either quality, price or (in the miniscule case of the Sony), reliability.
So figure out your set size, educate yourself on whihc features adn dazzling gewgaws are your must haves and go find your best deal on a new in box (no demo models) set at your favorite electronics store. Make sure to check out the widescreen functions in the store before you commit. Some brands use different widescreen scaling on 4:3 pictures. My Samsung (and most others I think simply stretch the image horizontally to make a braodcast tv picture fit the screen, wheras the Panasonic stretches the edges more than the center. Sounds weird, but it works really well...the people in the middle are less fat looking on the Panasonic and I never notice the different scaling unless I'm watcing a stock ticker or something.
Go here for good info and probably some model specific owner experiences.
http://www.avsforum.com/avs-vb/index.php
Personally I avoid extended warranties...its a roll of the dice, but the odds are very much in your favor to get a good set. Still, someone has to get the bum set. The odds are good that you'll have a failure in the first year or after 5 years, with the odds always going up over time that you'll have a problem...just like any other device really. For what its worth, only one of my Sony's at the bank has EVER even hiccuped in the 5 years since I deployed the original 18 sets. Bad power supply control board. All the others are still vibrant and crisp and run constantly...I'd say they all are in use at least 60 hours a week...some go over 100 hours a week.
To answer one of your earliest questions, dynamic contrast, see this thread on highdeforum.com
http://www.highdefforum.com/flat-panel-tvs/58167-what-dynamic-contrast-ratio.html
IMHO the picture quality on plasma still cannot be beat by LCD, at least not at similar price points...given the same HD signal the plasma will generaly spekaing always have the superior picture. I'm not talking sharpenss here, rather I'm talking about color quality, specifically the production of black. Plasmas can produce a true black and LCD's cannot...they get close, but the black is really just a dep shade of grey. You'll probably never notice it unless you have them side by side (like I do), just throwing it out there.
Lastly I would check with the store you purchased it from and ask about their return policy. Most places have an instore 30 day defect return, Best Buy has a 30 day "I didn't like it" return policy. They'll give you a ahrd time about it, but you cna return a perfectly good tv within the first 30 days and exchange it for a different one. Sometimes no matter how much research and planning you do, you just don't realize that you bought the wrong product for you until you get it home and put it on the wall...you may find for example that a 37" tv is far smaller than you really thoguht it would be and that you might be alot happier with a 42" set instead. I'm advocating trying to screw the store over or anyhting like that, just saying you never know...and when you're dropping 800-1000 of your hard earned dollars on a tv set you better make sure you're really happy with it.
Sorry to drone on an on. I'll stop now. Hope it been more helpful than tearfully boring.