Worked with a guy who has one. Runs on a schedule when everyone's at work. One day his dog got into a bag of almonds or pistachios. Ended up shitting everywhere in the upstairs room. Then the Roomba ran its schedule and spread shit everywhere. He had to clean up a huge mess plus buy a new Roomba.
Computer time...
When they did "Moon" with Sam Rockwell the director got quotes for effects done in CGI and quotes done with actual models. It was unbelievably cheaper to do practical than CGI. Got a guy who worked on Alien as well as Outland.