My iPhone's screen met its demise at the hands of a mixture of good ol' gravity... and pavement. It remained serviceable, yet I put myself in dire risk of cutting my fingers to shreds was I run them along the crack's vector. Given that there are no Genius stores in my area, I decided to have a crack at it myself.
The repair went well. Removing the cracked glass from the frame was fairly complicated, as there were bits and pieces of glass flying in almost every direction as I used the spudger tool to remove it (along with the old glue), but the task was successfully completed after about twenty minutes of muffled cursing and hair dryer usage.
All I can say is... be VERY careful with the LCD screen while removing and handling it. It seems that I acted a bit careless at some point since the LCD screen refused to work upon my assembling the iPhone together at the end (it displayed pure white with a large blot of dead pixels as dressing). After some not-that-muffled-anymore cursing on my part, I thought about purchasing the whole LCD screen+Front Panel Kit combo, yet I couldn't stay without a phone any longer and it would be a few days before the parts arrived no matter what shipping option I chose. Therefore, I'm now the proud owner of an iPhone 4S.