I have one. Well, it's not technically a Airboy, it's a rebrand from Nordblast:
http://www.nordblasthome.com/en/
But it is the same product.
I haven't used it very much, but tried it on some different materials. It does clean up aluminium and such very nice without any damage to the object. It also does remove paint from steel good. It does nothing on rusted steel or oxidisation on aluminium.
The one thing I can complain on is that it is not as quick as shown in the videos. This might be due to technique or the compressor I'm using (a single phase 240V, rated to about 2kW) or even the filter and hoses I'm using. It also uses a lot of blast media. I will continue to experiment with pressure and nozzle settings, but as it is now I fill too often...
The blast media is pricey to get. I bought a 25kg bag of Armex standard media, and with shipping that cost me more than the gun itself.