It’s very easy to use a computer LCD monitor (with DVI inputs) as TV by simply plugging in an HDMI to DVI cable. Of course, you will need a separate sound system/speakers unless your LCD comes with speakers too.
Of course, it’s also easy to do the reverse, using your HDTV as computer screen, you will just need an HDMI cable from your graphic card to the HDTV. (all HDTVs have HDMI inputs)
LCD TVs have come down in price, but not enough. If you have a cable box, than your tv tuner is in the that box, not in the tv, so then why buy a tv with a tuner you will never use? Believe it or not you can save almost $200 when you buy a computer monitor instead of a tv.
Also see what is HDMI here.