Kev are you sure the batteries are not lithium, if I remember rightly the old bosch sds's with nicads were 24v and had the square batteries. the 36v's that came in 2 different sizes were always li-ion batts, firstly they were 2.6ah, then they bought out the 4ah...the larger "full fat one (gbh36vfli)" was a great drill, I still use mine most days, the position of the handle to the motor made it quite unbalanced for one handed use though, I assume this is why they have now followed trend and gone with a drop down motor design.
the new Milwaukee fuel sds's look great on paper, not sure how much I trust the amount of abuse these new brushless tools will take will all there chintzy electronics inside them compared to a good old brushed motor though, time will tell. Plus there now made in PRC, the older bosch's were made in Germany.