Well, I've followed this entire thread and it really piqued my interest, so I just got back from buying an impact screw driver. I went with Ryobi 18 volt, since I've already got about 12 other tools that work on that same battery (and six Li-On batteries).
It looks and feels good, but I've wandered all over this place and can't find one place where I need to drive any screws today. Guess I'll just have to wait for the opportunity to arise.
It has been some good reading, good information and I really liked all the differing opinions on manufacturers and all.