I have dropped my iPhone multiple times (I know... you've all done it as well). This final fall was about two feet - from a shelf to a counter. It landed in just the perfect spot (some built-in Apple flaw) and shattered the front glass into a million pieces.
The repair went smoothly. Took about 45 minutes (most of which was spent picking tiny pieces of glass out of goo) without any complications. With the awesome toolkit provided, I didn't even have to use heat. I saw many accounts of heat warping the plastic, so I was happy to stay away from that.
One thing that the manual didn't mention was the protective plastic on the new glass. There were several sheets that needed to be removed prior to installing it. I was a little hesitant to remove it, but did, and it was the right choice.