When our oldest turned 14 we decided he deserved his own phone. He'd taken care of the hand-me-downs he'd had through the years without issue, an iPhone 3Gs and 4 survived without issue. Within a month of us getting him an iPhone 4S for his birthday he was the "victim" of some horseplay while waiting for the bus at school and the phone fell to the rough pavement face-down. It shattered the screen pretty good but still worked good enough so that he was able to use it until Santa could get him a new display. Santa did leave it for me to install though!
The repair went well, I've followed quite a few online guides from replacing complicated suspension systems in a Mercedes-Benz to Nissan timing belts and this guide was far and away the easiest to follow... the screws where A LOT smaller though! There weren't any deviations from the guide other than the way his screen was shattered quite a bit of the remnants were left behind stuck to the adhesive around the button and speakers so I had to make sure to scrape those away.
I had a piece of tape that I stuck the screws on and it worked fine but I think those magnetic mats that you can write where they came from would be very handy for future repairs.
I can't figure out why it was recommended that I buy the phillips #00 and flathead 3/32" tools with this repair, I did not need them, they are much too large to use on any screw in the iPhone. Luckily I purchased the liberation kit and the tools in there along with a smaller flathead I already had were all that I needed.
iPhone 4S Screen
Phillips #00 Screwdriver
Flathead 3/32" or 2.5 mm Screwdriver
iPhone 4/4S Liberation Kit