I'll chime in with some other thoughts....
I don't have any recommendations other than what everyone else has said.
I do have a little Hitachi impact and driver/drill kit and it works well (Li-Ion). I will say Hitachi does make a couple different models of drills in the 18V Li-Ion series. They have one that is 18V 1.5Ah and does not have replaceable brushes. They also have one that is more expensive gives you 2.5Ah batteries and I believe has replaceable brushes (or so it appears to.)
Also on the "batteries cost me a fortune" thing:
Some place like this:
http://www.batteryspace.com/
has basic Li-Ion/Nimh batteries that most of these units use. IE: my Hitachi impact driver unit uses 16850 Li-Ion cells 1.5Ah...I can get 2.4Ah cells $8 a pop (I need 3). So for half the price of a new battery I can rebuild one with 50%+ more run time.
Just a thought since everyone on here seems like a tinkerer..