I have a 50" Sony LCD TV (KDS-R50XBR1). Not specifically Mac related, but I had tried to hook up my PC to it a while ago, using a dvi->hdmi cable, and ran into a lot of problems.
First and foremost, most TVs aren't designed to be used as computer monitors; there is a difference in the way they are designed I believe so the picture won't look anywhere near as good on a TV as it does on a monitor - the TV is designed to look good for constant motion and be slightly blurry I think to keep video looking good (to prevent jagged edges anyways), whereas a computer monitor is designed for crispness of the image. That's what I've heard anyways. My tv does have a VGA input as well, so I guess maybe they can optimize themself for PC viewing.
Whatever the case, I ran into a lot of problems. First and foremost you'll normally run into overscan, having to tweak the video a lot or use a 3rd party program to keep your start menu or menubar from being located off of the screen.
Next thing I ran into was kind of what I described above - the desktop looked like crap. Once I ran a video file and played it, it looked pretty good - I was a bit confused by the desktop looking crappy but video looking fine, but like i said above I guess that's just how it is.
So from my experience, I wouldn't recommend it. Newer tvs however might not be as bad, or the VGA port might be better optimized. I know at work we have 42" Dell plasmas and they work a lot better, but the resolution is still not very high and it makes it hard to do anything. In most cases a good monitor closer to your face is always gonna be a better choice.