Most of the TV-LCD things are fairly bad quality LCD screens (dead pixels, lousy contrast, washed out colour at best, low resolution for PC side of things......) with a component in as you say until you pay good money (at which point you may as well get a normal screen and a TV tuner of some form). Take a walk around a costco/walmart or something and you will see (the small screens they advertise random "inventions" tend to represent the better ones which is saying something).
Ratios: some are bad but most of the time they are OK. PC screens tend not to be TV ratios (16:10 vs 16:9 kind of thing) but a PC should not have a problem.
My advice: buy a decent LCD (which will likely not be that much more if it is as all) and a firewire tuner (firewire as USB ports are more valuable I find) or better yet one of those little all in one player boxes I have been seeing around lately and a switch if needs be.
LCD tvs on the other hand occasionally have a PC in of some form (or if you have to DVI via a HDMI port or something) and those are quite good, they are not usually quite as high res as a dedicated monitor but they are good.