I've got a bosch 12v drill, I've given it some stick, but it's doing ok. it's light and very comfortable to use, but it's not up to the bigger jobs.
I made an adapter to run it off a battery, which works well. Of course a 12v battery is at more than 12v most of the time, and the drill reflected that by getting warmer much quicker than on it's own battery power, when used for longer periods of time.
My advice would be, if you want to power the drill of a vehicle, to get a 14.4v drill.