Fell with iPhone 4 in hand, hit the ground face first. Entire front screen shattered.
First time with iFixit (but I won't lie, I kind have always wanted to take apart my phone, I'm a bit of a tinkerer, so I suppose my unfortunate fall was serendipitous).
As for the repair, I watched the video first and went over the instructions a couple of times before I got started. Which I highly recommend doing.
First, not including my preparation of watching and reading first, I would say it took about an 1 1/2 hours. The guide is excellent and the PDF print out for your screws and parts is amazing (seriously, use the printout, don't know how I would have done the fix without it.
Went step by step. I will say though, my model had the ridiculous amount of glue, so it took some prying to get that out, slow and steady prying on all sides of the battery. As for the rest, everything was pretty straight forward (read every bullet point on the guide).
Oh and take off the blue plastic covering the mirror on the back of the screen, in the video, it appears that she left it on, but I took my off.
Overall, step by step, it was time consuming but if you followed the images and don't mind messing with hilariously tiny screws, it was a fun experience.
The only downside was when I turned it on, the screen was gorgeous, but I had a deadzone on the left middle side. Every other part of the screen was responsive, except for that section.
But of course the great folks at iFixit sent me over a replacement screen right after I emailed them (thanks a bunch guys). So going over the process twice now, screen works wonders.
Some advice, first that iPod plastic opening tool, somewhat brittle, my tip snapped off while I was trying to pry up the battery. So be gentle, like I said, slow and steady (no innuendo, I assure you).
Second, wear gloves, I used a pair of latex, with all the warnings of getting greasy finger tips on connectors, figure better safer with just keeping gloves on.
Also, when in the end I was trying to lift the screen, I found it easier to start at the Dock end of the phone to slowly pry it up and work my around the metal frame.
Finally, be vary careful getting the connectors through the frame, follow the video and make sure you don't get them caught up, and also when it comes wifi antenna, careful with the part that the 4.8mm screw goes into. It takes some delicate work to get the whole antenna out it out, even more so to get it properly back in.
Don't get discouraged and don't lose patience, those two little clips at the bottom are not insurmountable. :)