I had the same thing w/ a milwaukee 12v drill. I got it about 11 years ago and both batterys still work!! So naturaly I got the milwaukee 18v kit and the thing was a piece of poop. Heavy awkward drill and got maybe a year before one of the batterys wouldn't charge at all. Never had bad luck w/ Makita though.I will agree with XanadooLTD. The Hilti's and Festools are awesome. I would follow that with the Makita line. I have an ancient Makita 12V with the stick battery that I just keep in my home shop. It just won't die! It took a serious beating in its day before I switched to higher volt/newer style drills. I also have an older DeWalt that has held up great, other than replacing the brushes. My current go-to is a Milwaukee V18 set that I got for a steal, and an M18 compact set that I am quite pleased with so far. I have not had any problems with the Milwaukee stuff, but I keep thinking I should have saved the money and put it toward a Hilti or Festool set. Milwaukee batteries just have a bad reputation. Panasonics' are also nice. Great balance and feel. I only have experience with using their older NiCad tools, though. I don't know much about their Li-Ion.
Take into consideration how Hilti cordless rank. Hilti's 18v liion drills are about an american 24v. So you will not go wrong with the Hilti's. You will get insane power and light weight. Good move.I use a Dewalt 18 volt xrp for daily use, the hammer drill and the impact. Both have held up pretty well and the power is great, but after about a year or so the batteries seem to dwindle as far as max power and how long they hold the charge. I may tryout a makita if the price is right but I have been very happy with my 6+ cordless dewalt tools
As for Hilti, we have a dry core rig, a couple powder acuated guns, and 5 or so rotary hammers and they are all awesome. I cant wait to try out their cordless drill line, thats up next.