Hey, Josef!
I agree that Kamal is simple, but with capistrano I had no such problems I had with Kamal. I had a couple of conversations with devs from different communities and some of them stuck with Kamal configuration.
PS: Thanks a lot for your book, I've used it when I stuck with Kamal 1, it helped me a lot about a year ago (but there were some issues, not sure that I can remember details).
Kamal is relatively simple tool. If you understand a bit about DevOps and what Kamal can do things are pretty much smooth.
If you never did anything with servers and suddendly want to deploy with Kamal? Then it can be painful.
For those that want to take Kamal for a spin I wrote Kamal Handbook. No self-torture required.