You definitely want a true 1080p TV. That'll have 1920x1080 pixels, which is slightly less than a 24" computer monitor. Many 1080p TVs have a computer input for DVI, but as long as it has HDMI you'll be able to connect it to a computer with a DVI-HDMI cable adapter. Next, I'd look only at 120Hz displays. 60Hz is usually more than your videocard can display at 1920x1080 anyway, but I'd rather have more room for growth. Finally, an LED-backlit TV would be an ideal choice. All of Samsung's 950-series TVs have all of these qualities, and they come in as large as 55".

However, you need to sit far from it for the text to be crisp, so don't put it 2 feet in front of your face. I'd personally rather have a 30" Dell (2560x1600 resolution) than a larger TV as a computer monitor, since you'll be able to sit closer to it, have a much higher resolution, and cost a lot less.