I work my cameras daily as well and while I take excellent care of them I am not afraid to take them into some rugged weather and grueling terrain. (rain, snow, hot, dry, dust, pollen, humidity, etc... cameras are tools for me) After several years of use I recently sold my 5DII and 1DIV for the current models and the only thing that was a detraction were the scratches and wear on the lcd coatings. Nothing serious, but when someone buys a new camera that is one of the top questions and comments.
Also, when using in bright sun it is much more difficult to see through even a slightly scratched lcd then a clean and clear one, and I dont want to go through the effort of replacing the panel that canon includes. My iphone has a nice static protector that I replace every 6 months and its like I have a new phone again. Thats what I am going for here with the camera.
And lets face it... many of us sell our gear and upgrade, and while resale value is not a consideration for me when I buy a camera, it is nice to have as much value in a camera when it is time to upgrade to the newer and more technologically advanced tools.
Personally I have never worried about protectors. The glass Canon uses is spectacularly tough. The only thing to watch out for is the possibility of the camera banging against a belt buckle for extended periods. Even this may wear through a protector in quick time.
But in general use, working my cameras pretty heavily on a daily basis, I've never scratched a screen. I smashed one on a 1Ds many years ago which CPS was kind enough to fix for free while I waited.
Don't sweat the small stuff...just enjoying your camera without wrapping the whole thing in cotton wool. They're tougher than you'd think.