Pretty much agreeing with what has already been posted. Always pays to hold off on the newest/most expensive tech--LED and 3DTV. They are only going to get better and cheaper. Definitely wouldn't touch 3DTV until they get some material released for it.
Plasma vs. LCD comes down to personal preference and if you have a lot of light (there are ways to control light--room darkening curtains, etc)
You'd really have to try and cause burn in. Like already mentioned, you'll get some image retention--but it goes away quickly.
I'm a plasma fan--cheaper, darker blacks, no motion blur, wider viewing angles.
My rule for buying a HDTV. Set your budget. Then get the biggest name brand tv within that budget.
Other things to consider: number of HDMI inputs, PC connection, USB connection.