I might be wrong, but think my impact driver will be the least used of the three for screw driving..
Well, sorry to resurect an old post, but I have to say how wrong I was...It's now one of my most used tools. A decent hammer drill will put a big screw in, but the effort it takes to keep the bit in the screw and to stop the drill trying to break your wrist is huge compared to using and impact driver
I;ve used it OS much for scewing it's unreal...I only use a drill when the impact is going to be too noisy, but I notice the difference now!
My 2 yr old loves to 'help daddy' and i some times give him 5 or 6 4" screws to put into a piece of scrap...I hold the impact driver in the screw head (quite lightly) and he holds and presses the trigger...he loves it. He has also (just) managed to put in 1.5" number 8 by himself (i started it obviously)...so a tool so effortless in use even a 2yr old can use it