I have several Derringers. Back long ago now; in the early 1990s I carried a Davis .38. I did not have a lot of money for a carry gun back then and the Davis was cheap... $60 if I remember correctly, and small with enough power.
I have put thousands of rounds thru my derringers and while they are rather unique... they are really not that much different than other single action revolvers. The main thing for me was to remember which way the safety pushed. It took time to get use to the way it shot and handle the recoil. I spent many enjoyable hours shooting my .38, usually a box of 50 rounds a session. Hehe takes some getting used to loading only 2 rounds at a time.
The main drawback was you had to draw, cock and push the safety off... a lot slower than drawing and squeezing the trigger on a Glock.