I use a 42" Sony LCD TV as the monitor for my Macbook at my office desk, via an HDMI cable connected through a generic / aftermarket converter to the Macbook Mini Display Port. Works perfectly, with no lag time that I can notice, even when using the mouse quickly. Only problem is when booting up computer you need to mirror the displays, starting with the Macbook screen. That computer stays on 24/7, though, so not a problem very often for me.
I tried using the same TV, which is also connected to an AppleTV, over Airplay (wifi). While this works perfectly for watching movies, videos, etc., that are on the Mac (or also any iOS device), the lag time for typical computer work involving mouse and keyboard was just annoying, so I switched to the system above.
I am considering installation of a Windows-based Home Theatre PC that would connect to this same TV (because I can't find a way to use a cablecard tuner with a Mac solution that lets me connect to other TVs via IP, unfortunately) and will also use a straight HDMI connector for that.
