Bought one of those a few weeks ago and put it to use at my sons house driving dry wall screws through OSB. I normally don't care for cordless tools but that thing has impressed me. I already had the 1/2 inch electric drill that will break your wrists if you let it so I decided to try this one too. It was expensive but it works very well.

 

I've got two of them, and they're awesome. One of them I've had for about 4 years, the other about a year. The second one came in a kit with a circle saw, a recip saw, and a flashlight--I bought the kit to get the batteries since the original ones had gotten pretty weak, plus they had a deal going at the time to get two more free batteries if you bought a kit. The cordless saws have quite a bit of power, but they do run the batteries down pretty quickly. Still, they're awfully handy for some stuff since I don't have to get the Porter Cable or the big Milwaukee worm drive out and run cords and so forth.