I've done it a couple times. I did it for the 2015 Dopey and 2015 Dumbo Dare Weekends. I used the head strap both times.
For me, the nice part was not having to worry about holding the camera while I was running. When I watch the footage on my computer/iPad, it gives you a good eye-level view of what running the race is like. Plus, when I go on the treadmill when the weather isn't ideal, it's something fun to watch and feel like you're running the race again.
However, there are some downsides that I encountered. One is that having the GoPro on your head while running is somewhat awkward and can feel like you've got a little extra weight on top of your head. Another thing is that the battery on them is OK. For both 10k's, I was able to record the whole running of the course, but I bought a better battery compared to the one that normally comes with the GoPro. (Just do a search on
Amazon for GoPro batteries...) The amount of recording that I got with the battery was no more than 90 minutes.
Also, with having the GoPro attached on my head, the footage can be a little bumpy. If you going at a nice easy running pace, I don't think the shaking would be that bad. When I did the
Disneyland 10k, I ran between a 8:00 to 8:15 per mile pace (not trying to brag or anything...) and it was a somewhat bumpy. But I was able to use some software to stabilize the video that makes it a little easier to watch.
I'm actually in the process of putting together the Disneyland 10K race footage and uploading it to
YouTube sometime this week. When I'm finish, I'll try posting a link of what the footage looked like.
Good luck next month with your 5K.