I wonder what members' experiences have been with the use of a power screwdriver on a bike. When I was outfitting a bike for a family member, making it usable in everyday life, and needed to cope with a number of bolts (fenders, rack, rack, reflectors, lock mount etc.), I turned to a power screwdriver. This has been an impact screwdriver from Sears, where the impact mechanism could not be switched off nor the torque, otherwise, regulated. For smaller tasks on a bike, I have not been using much such a screwdriver.
Also, can anyone recommend a source for metric hexagonal bits?