I hook my MacBook up to my very old SDTV with Apple's DVI to Svideo connector.
For playing full screen movies from Quicktime and DVD Player - it's fantastic. I just watched a movie last night, in fact, from my MacBook. I watch Quicktime movies all the time like that.
One oddity - maybe just my TV or computer - the image is slightly off center, towards the left, so a DVD plays back with a bit of black bar on the right side. Can't remember if it does it with Quicktime movies too.
Using the TV screen as a computer monitor is going to be impossible. It literally looks like you put a thick coat of Vaseline over a regular monitor.