Just a couple of things to consider.
If you are sitting (up) to 12 feet away then a 32` or 37` will do you fine. Anything bigger and you will start to notice any artifacts in the picture. Plasmas have been labeled HD ready, newer models are labeled Full HD. If you have no plans to pay for HD channels in the future then its not worth paying the extra for a Full HD set. Do not be taken in by the high quality of pictures that are on display in the shops, some of those are being fed through an upscaling video converter that would cost as much as the tv itself. dont be rushed into buying something based on the sales pitch that those spotty faced kids give you. Believe me if you bombard them with technical questions they go red
and then run off.
First rule of thumb,the picture will only be as good as the signal going into it, although you should see an overall performance boost with a new LCD or Plasma.
Most plasmas are set to factory default settings when you get them ie: brightness, contrast, colour whilst some of them come with different settings for you to adjust, you can if you want get the best out of it by spending an extra couple of hundred bucks on getting it calibrated by a technical engineer, but thats optional.
Try and visit somebody who has got either an LCD or Plasma and judge for yourself.
Panasonic is a brand which has sold well in the uk, its also a top seller in the states as far as I can see.
Have fun whatever you get