Indeed they are. In my opinion, they're one of, if not the best invert a beginner can keep. They have lots of personality and most species aren't very demanding.
I've kept ghost mantises and european mantis in the past, and I currently have a Polyspilota griffinii that my LFS randomly got in. Mantids are really amazing creatures! I'd love to try violin and orchid mantises at some point.
I had one when I was a kid, after that whenever i'd find them, i'd just leave them alone or pick them up and appreciate them for a few minutes then put them back so they can kill more pests