I have the Zagg Invisibleshield (form Radio Shack). I installed it myself, it was petty simple. It works like a charm. It covers the whole front of the phone (minus the camera and the top earpiece, of course), and it really doesn't take away from the phone looks at all. It protects from smudges, too. I mean, sure, it can get them sometimes, but not nearly (and I really want to stress nearly) as much as just a plain screen.
Function wise, it protects from scratches very well and I can still use the phone as well as without any sort of cover.
As an added bonus, if it ever does scratch (I mean the cover, not the phone, the phone won't) you can peel it off (oh, it won't peel on it's own by the way) and sent it to Zagg and they will send you a new one no questions.