if you do some searching around the forums, you'll find that not only do plasmas usually introduce the lowest levels of lag out of LCD DLP, also because the plasma is phosphor based it runs the potential of IR or even Burn in, CRT's also carry the same risk. If you weren't worried about your CRT burning in, i wouldnt worry about your plasma. Plasma has made leaps and bounds concerning the IR issue, and as long as you treat your plasma nicely it will return the favor. I would suggest (dont have to) that you give a standard 150 hour break in period using either the break in images (search for em) or making sure you keep the black bar content to a minimum.
game all you want when you get it, just dont pause it for a day. people always freak out about gaming because in games like Halo and such there is a HUD, and that tends to be in the same portion of the screen always. but what people forget is that unless you sit in on spot, not being on pause, that HUD is on and off between cut scenes, between matches (assuming online play) pee breaks. Even in games like guitar hero where the little box is on the right, your constantly goign to the menu between songs rendering the HUD myth foiled.
Get a plasma, you wont regret it, LCD's are good for like digital picture frames where stuff isnt moving, they really excel there.