I'm an amateur and used these when wiring a new construction. It took me a few minutes to figure out exactly how they worked, but I got the hang of it soon enough. However, closing the clamshell can be hard on the fingers if doing a lot.
Also, I had two bad connections out of 20. It wasn't worth it (to me) to try to rewire the bad keystones. I cut them off and pitched them in the trash, replacing it with new ones.
Considering the price and results, I'd use them again.