There are tons and tons of projectors with resolutions all over the place. You can find cheapies with 800x600 resolution (which is just fine for NTSC standard definition), or if you spend the big bucks, you get true HDTV resolution projectors that have native resolutions of 1280x720 or 1920x1080 (really big bucks for a 1920x1080 native unit). Actually the price of some 1280x720 projectors has dipped below $1000 now, which is cheap for HDTV resolutions...
If you're going to use a projector as your main TV, be sure the room is dark even during the brightest of days. Like Ironrice said, the main drawbacks are the need for darkness (a non-windowed room rules here), and mounting. Remember the screen you use will reflect ambient light as well as light from the projector, so be quite sure you like to watch TV in the dark before you go this route. At least with LCD/DLP projectors mounting has become less of an issue since they are much smaller and lighter than the old CRT projectors.
How much help did you want?
http://www.avsforum.com is where I go whenever I'm looking for HT information. Some combination of those guys literally will know everything.
Finally, it's just hard to beat a direct-view TV. The picture quality on direct view is great, the viewing angle is much better than rear-projection, and there's no need for relative darkness like front projection.
Anyway, go to
http://www.avsforum.com . Those guys know way more than I do. I believe Ken and Clint are on that board as well.