The LaCrosse has test modes where you can put cells in, it charges them up, then runs them dead again, then charges them up, and tells you how much actual power it got out of them during the discharge phase.

It's also useful to see how much power went into each cell during the normal charge. If I have 4 matched cells, they went into my taillight as a group after having all been charged, and every time I charge them I have 3 cells take 1600 mAh of charge and one takes 2200, that one cell is probably about to bite the dust. I put a mark on any cell that charges abnormally like that, and if a cell gets enough marks, I chuck it in the recycle bin.