I've heard different stories about temperment.
One account, I've heard they've got the temperment of a Niger.
Another account, I'm heard they're as bad as Queens.
Everything I've found, they'll grow to at leat 12" long and are definately not "reef safe".
I've never personally owned one, so you can take what I say as a grain of salt. It'll vary from person to person.
They've rare enough, you're not gonna find too many people who own then. However, less then a year ago, they were selling for $1000 a pop...now, they're down to $250 (even less, on some sites).