DeWALT makes some of the best powers on the market. The brushless DCF886 impact driver is one of our favorite 18/20V impact drivers, but lacks speed control options. The other option has always been the brushless DCF895, it has 3 speeds and the hex chuck is built into the head making it great for tight situations.
The DCF887D2 looks to be the best of both current DeWALT impact drivers. Speed 1 also acts as a precision drive setting. Check out the DCF887D2 on Dewalt.com. Look for a video on this soon.