I've seen some amazing things and this is one of the most incredible
I know a lot of people who are into this kinda stuff, including a few who actually built them. There's a whole online community of people who build them, too.. It's a fun high voltage project if you can get your hands on a 15kV power supply and a diffusion pump, and it isn't that dangerous as long as you use proper shielding and ground everything properly. I hope they weren't standing next to that geiger counter that was reading 50k cpm for very long, though.
Also, it's unfortunately impossible to get net positive energy from fusors, but they can apparently make pretty good neutron sources.