Check before you commit. I also find that TVs have too low of resolution for my tastes/eyes. I like really high resolution. A TV gives you a lot of size, but even a 1080P signal is not high resolution in the computer world. I'm typing this on my MacBook Pro 15" and its running at 1680x1050 on the 15" screen. There is no real difference between the 1050 that my MBP has and a good 1080P TV, yet the TV is going to be a lot bigger.
I agree with all the previous posts. I have a mac mini I use as a media server computer. It works great for the video aspect of things, but going through applications that aren't designed for TVs is annoying - too low resolution.