I've had the Makita 12v job a bit now, and it's really something. I
had reservations that the impact portion would be hard to work
with....it's not! To me, drilling holes is just the same as with a
regular drill. You will need drill bits that have the hex end on
them. They are a bit more expensive, but affordable.
When driving screws, as you encounter resistance, the impact portion
of the driver kicks in. It slows down a bit, but the impact protion
is amazing. There is a HUGE reduction in camming out screw heads.
The torque is incredible. I have not used it to drive into concrete
or metal, but I would assume it would be just as easy. The only point
of caution would be as you drive the screw, you have to release the
trigger, or you'll keep driving the fastener right on the the piece
your working on!
My decision came down the the 12V makita and the Panasonic impact
driver. Besides cost (panasonic ~$100 more) the 'keyless chuck' for
the panasonic looked cumbersome. The fit of the makita is outstanding
and I have huge friggin hands. I also live close to a Makita repair
station, so if something lets loose, I can go there for repairs.
All in all, I recommend the impact driver. If your work is only on
woodworking, save the money and get a nice 9.6 or 12V drill. But if
your at all going to use it to put together a deck, or install stuff
in concrete, go for it baby!
P.S. One drawback for the impact drivers are the noise. When the
impact portion kicks in, it gets kinda noisy. So the baby is sleeping
upstairs, you might consider a regular drill.