Skein,
They are pretty popular in the marshes around Klamath Lake. I've seen guys crossing the big parts of that lake in windy rough conditions and a Go-Devil (also a brand called Beaver Tail) can boogy along. Power doesn't seem to be an issue.
There are different hp ranges.
Have you checked
http://www.go-devil.com/ ?
If you want names of users, I can check with some of the K-falls boys.
I have no first hand experience.