Well I checked and it outputs up to 1A so that's covered but as you say there is no real way to know it's acceptably regulated. I assume that to work with USB devices it has to meet some voltage range specification much like the USB ports out of the computer, therefore I figure it should be ok.... ?
Edit: Looking at the gamma1 website it looks like there are voltage regulators on the USB port anyway so now I'm really not worried about that. It looks like it needs to be regulated if I want to use the power plug.