Projectors are good for low resolution, low light, and low cost for a potential big screen.
Unfortunately i don't live in a cave and im usually viewing 1080 content.
Unless you are spending big bucks on an HD projector, you are far better off with a TV.
Depends on what you do, plasma is great for movies and darker environments.
The new LCD LED backlit TV's are now pretty cheap, they are bright and use way less power that plasma and even CCFL LCD's. My LED backlit 42" in the bedroom uses less power than my 26" CCFL LCD, believe it or not.
Projector bulb life expectancy is typically 1,000 to 2,000 hours for metal halide lamps used in medium to high end projectors and 40 to 70 hours for halogen bulbs used in most low-end to medium priced projectors.
You will need to factor in the cost of replacement bulbs depending on how often you will be using the projector.