I'd read about them in several of my books - generally the gist of the articles said they were impossible to keep with other tankmates, but were great for species tanks. And they looked so beautiful and cool!
Eventually a guy in my reef club posted that he had one that came in on some rock, and since I had an extra tank sitting around, I took it. I'm on my second one now, and if I had room, I'd set up additional tanks and get more. They've got great personalities, and I really love having Gojira next to me at my desk.
I guess the main thing I've learned is do regular water changes. My first one had a bad molt - perhaps because I didn't do enough regular water changes. The other thing is to give them the appropriate food - hermits and snails work great, though they get a bit expensive if you don't live near the ocean. For feeding, I've found the thing to do is keep a second tank, and order larger cleanup crews every few months. I just pull a snail or crab from the second tank and feed it to the mantis every day or so.
Ken