I used these as well. They were more of a pain to install than I thought they would be. Seven of the eight went it fairly well, but one just completely blew out the hole I drilled.
You do need to be careful. A trial installation in a piece of scrap wood is a good idea if it is your first time. The hole has to be big enough to accept the insert without making the MDF bulge, but not so big that the insert's threads barely grip the sides and rip out the MDF. I've made both errors, but I still like the inserts enough that I wholeheartedly recommend them. If you do blow out a hole, then the fix would be filling it in with some sort of epoxy such as JB Weld and then drilling and reinstalling a bit more carefully. For bulges, unscrew the insert, drill the hole deeper or wider as necessary, vacuum it out, reinstall the insert, and sand the residual bulge down flush with the rest of the CP. Once you figure out the proper hole diameter and depth on a scrap, it is very easy to replicate without issue as many times as you need to. Of course, some of us think we can get it right the first time and then we have to figure out a way to repair our nearly finished CP...
--edit--
I almost forgot. Be sure to test your final screw length in the scrap as well. It would be very easy to use a screw that was too long and create a bulge that way. Of course, you can also buy screws that are too short. My inserts sat further down in the hole than I originally accounted for.