I've thought many a time about these, and due to the torque alone they're a much better option than what a typical 18V drill can put out. They're just awesome on the jobsite for any kind of screwing (hey now). The Bosche I was using the other week was driving 3/8" lag screws in like they weren't even there - with no pilot holes.
The one thing I'm not 100% on is how they would react if the auger encounters resistance and it flips to the impact mode. The drill has a constant, linear pressure on it's rotation, where the impact will pause and then slam again. It's the rate that it's doing this that has me concerned when you apply it to a
"shaving" style of auger. It may hurt it a lot less than someone repeatedly slamming the auger around at the bottom of the hole or leaning on it the whole way down like I see some guys using their augers.
If I had an impact at home and something like a cheap Mora that I wasn't worried about (rather than a Nils or Lazer) I'd be a lot more interested in how it ended up. Would be really neat if someone made a chipper style auger blade in 5" - I bet it'd work great with that style of head.