I certainly do. I’ve found bugs, submitted patches. I not only understand the math, but have written libraries and tools, audited cryptographic implementations and frequently communicate with other developers and engineers in the field.

I have developed educational materials for folks and played with this technology a long time. I will admit I don’t grok every line of the science experiment geth (ethereum client), but I do understand the math, it is the same as Bitcoin. I haven’t been keeping up with Eth client nearly as much as BTC. Running an eth full node needs some real hardware. BTC runs on a potato.