Personally I'd only use a Mains powered Hammer drill and more often than not it would be a Hilti.
I have a TE-50 that gets quite a bit of use.
With respect to cordless drills, I use a 14.4V Panasonic drill unit.
I've drilled through wooden power poles using an Auger bit with this drill I don't know how many times.
The biggest issue though with this drill, is not the battery going flat, but being careful your wrist doesn't get broken if it jams, mid-travel.
The batteries seem to keep a charge quite well too.
