I think the HoC's that get me the most are the ones written by JS devs who think 100% functionally. Actually a lot of the hard ones to grok were written by Jason Miller of the Preact fame, who seems to think out JS in a minified, functional fashion. I've had to step through and re-write several things just to see what was actually happening, then pare it back to it's original form before I "get it". It's super clever, but man did it take me a while to distill it's logic.
In the end it depends on what you're trying to accomplish. HoC's are pretty useful. Also, it really helps in terms of unit testing your more functional components.