if you want best overall picture quality, buy a plasma. no LCD/LED i've ever seen(which does not include some of the uber expensive full arrays that are no longer available anyway) has even been close to looking good in a dark room. LCD/LED is acceptable only in situations that require constant on scenarios, will only be used in very bright rooms, or where picture quality is not a concern(i have an LED in my bathroom for example).
do not buy an LED simply because it's available in a larger size. if you 'need' an image larger than 65" then the answer is front projection, not LED. there might be that small niche where you need a huge display to work in a very bright room, then the 80" led's make sense, but that's it. i'd still take a projector on a 100"+ screen with some ambient lighting that washes out the blacks over a 80" LED that never had blacks to begin with. and with some good control of lighting, you can certainly get plasma levels of picture quality with front projection. i happen to prefer the image on my jvc x35 over my samsung f8500. of course, the brighter the room, the more likely the plasma will look better.
so, to sum up
65" or smaller:
-get a plasma, never even think twice about
larger than 65":
-get a front projection setup if you can control lighting
-consider LED if it will never be used in the dark
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1018AH, 5.1 audio
Sources: HTPC(Mediabrowser), PS3, XBOX360, Wii, Sony DVP-CX995V
Control: Harmony One