It really depends on the monitor you are using...I hooked my DVI cable to my 27" and it would only show 1280x720 or 1920x1080 (HDTV resolutions). My VGA connection allows for different settings which 1360x768 looks the best and fills the whole screen.
People say it makes it look more crisp but honestly I really didn't see any difference. You will however see a difference in DVI and other connections with HDTV, that's a given