My wife dropped her unlocked (read $600) iPhone 4 onto asphalt while running and shattered the front glass into millions of little shards of glass. It was so bad that we had to put packing tape over the front to keep the glass from falling out all over the place!
The repair was difficult, but went great. At first, I was put off by the price of a front assembly being that it was more than double what other vendors sold the product for. Ultimately, the fact that other vendors look shady and got bad reviews, led me to order from iFixIt.
Great experience; gOt the part quickly with no issues. It took about three hours to complete the repair. Most of that time was spent cleaning the shards of glass off of the area where the front facing camera and light sensors are because there was a lot of glue there.
The repair was difficult but made infinitely easier by the wonderful online repair guide that was very easy to follow. I'd suggest having a white piece of paper near by and tracking which step each screw belongs with as you remove the various pieces.