If you don't get a bluray player or home theatre PC ,there isn't any point in going high end. Mine is a 50" Samsung plasma, only 720P resolution and looks awesome (plasma is also more forgiving in the lower resolution than an LCD would be).
If you watch low quality sources like standard cable/TV and even DVD's, A plasma is
much more pleasing/forgiving to look at. Since they have a reflective screen (usually) they will be a little more annoying if you have a lot of sunlight in the room while you watch TV.
The only thing you have to watch out for with a plasma is if you watch a lot of TV that has still images on it for long periods such as news/sports with the bar at the bottom, or certain video games with still images, or movies with black bars along the edge. For the movies you just have to zoom in to fill the screen so that you don't have black bars along the edges. Don't use picture in picture or split screen. Also with a Plasma, don't crank the brightness or contrast much over halfway and you will increase the life of the screen. Over the years the colors will fade (not nearly as fast as a projection TV) and you can slowly add a little contrast on the settings to compensate.
LED is just a type of LCD that uses LEDs for the backlight through a standard LCD screen. I believe the brightness is supposed to be more even throughout the screen (Never really noticed a problem in that area). I don't know if there are any other advantages other than they are also slimmer. Maybe somebody else here knows more on the subject. I don't think LED is worth paying extra for personally. I can't comment on 3D.
As you can tell, I really
much prefer the look of plasma if it fits your lifestyle. I can't stress the "much" enough
If you care for it, I don't think burn-in is a problem for most people. When I first bought mine, the contrast was maxed out from the factory. I played video games that had permanent bright images on the screen for long periods of time. I did burn in some of those images with the high contrast settings. Once I noticed the burn-in, I stopped playing that game on my TV and the ghost image went away after a few days.