Hi Justin, scary-assly, Makita have discontinued their 36v rock eater

All their rep had to offer me the other day was an 18v miniature wannabe
drill. Its worth checking that this is really the case as that was a good
drill and cheaper than the Bosch, Makita tools rock!
That said the Bosch is a really bomber
drill. You will be very happy with it.
The only one bettter is the Hilti TE6A (or latest equivalent) but at over ten grand for the kit its kinda outta reach of most mortals.
Retro fitting of drlls, with 2X 12v Alarm batteries, was something we did to the old 24v drills when their NiKad batteries died (which they did alarmingly quickly, scuse the pun!). It is not something I would recommend doing to the new drills as most have a slow start feature (
drill turns slowly at first, nice for settting the hole) which will malfunction without the correct power source. Replacing the batteries will also void any warantee you have on a new
drill. Over and above all of this the new InfoLithium batteries are really good, charging quickly and lasting way longer than the old NiKad ones. If you can afford a new
drill the Bosch is a great choice (probably the only worthwhile choice with Makita out). Investigate whether the Bosch has the option of a seperate battery pack, ie: one you can mount on your belt or keep in a pack, if it has get it as this will make a massive difference to how the
drill handles, holding a
drill and battery at arms length behind your head whilst hanging upside down in a cave is
not pleasant!!!!
(Point out to the sales rep how we use their drills, maybe if enough of us moan they will stop designing them purely for people who are drilling into concrete at their feet (faint hope but worth moaning for). The balance is all wrong for using them overhead).