The Panasonic sales rep was up at our Sears a while back.
I asked these same questions...supposedly they are rated for 50,000 hours, same as CRT
Plasmas eat a lot of power...put your hand over one. New source for heating your house!
Plasmas have a better contrast ratio because they can do true black. LCD is a white-light source filtered for the color they need to generate. Just a different and ever improving technology.
If you want 42" to 65" and money is no factor, go plasma. Otherwise, hang on as LCDs slowly go beyond 32 inch. If you have a chance, check out a 32" LCD HD TV...they are incredible.