I'm using an old Bosch that my grandfather gave me. It had ancient Nicad batteries, which I replaced with some super-cheap, Grade F (Powerizer brand) NiMH cells. Thus far, they seem to be working.
I had plans to refit one of the packs to use Li-ion cells, but I kind of lost interest in that project. Some day I might pick it up again though. The NiMH's are working just fine for now though.
And the drill is great to use. Long battery life, and it's got a lot of torque.
Dman: NiCads or NiMH's can get a "manual" charge, at least to boost them a bit. But don't do that with the Li-ion packs. They've got protection circuitry to monitor each individual cell. Plus, those things are somewhat volitile.
One possible way of reconditioning a pack of Ni-xx cells might be to break open the pack, and cycle the individual cells. It's possible that one has gotten weak over time, and that can bring down the performance of the whole pack. If it gets weak enough, it can find itself reverse-biased, and start taking a reverse charge from the stronger cells. When that happens, the weak cell will sustain damage.
My dream battery pack would of course be Li-ion, but it would use one of
these circuits, instead of a conventional protection circuit. Conventional ones simply
monitor the cells for excessive current flow rates, or low voltages. This kind gives individual charging attention to each cell, to keep them all at nearly the same strength.