"Are they otherwise unhealthy?"
Good question. I know they had health problems when the so-called breed was created. Honestly don't know their current status. Certainly hope they're more stable today.
I don't breed or show cats but I have a couple of very good friends who've been in "the fancy" for many years. They're highly legit, don't run kitten mills, and truly love the respective breeds they work with. I also know how hard they work to improve the health, strength and temperament of the cats they breed. So as you may imagine, I had a terrible time watching the carnival sales atmosphere at the TICA show I attended. Poor little Munchkins are breed on a fault. That's never a good idea.
I like the rag dolls, which were first bred for companionship.