Is there a reduction gear in that to protect against stalling the drill?
Nope, from the descriptions I've been seeing and from the video's posted, it looks like there's just a direct bearing to try and spread the load - but no actual gear reduction.
I'm torn on the whole thing - it does look like a nicer setup than my current drill/Nimrod setup, but I don't think I'd gain anything switching to this. Add in the cost of the adapter and a dedicated drill, and for not much more I think a gas auger is close (granted not top of the line, but still).
Thinking a gas auger would be a nice investment this year. Along with some transportation....