You're right, Drew. Beertools Pro keeps track and subtracts from your inventory.
I've used Beer Alchemy, BeerSmith, and Beertools Pro. BTP is the one that I ended up buying. For me, it was all about the interface. There's so much functionality in it that I'm barely scraping the surface. Bobby M from HBT has a bunch of videos on youtube about the different features that are really handy.
Josh, when's the last time you updated your copy? I know they added Carastan back in July. If you post on their message board, they're really good about adding stuff people request.
On Tap: Irish Red, Amber Ale, 80/-, ???, Oatmeal Stout
Fermenting: BBD Dark Mild, Session IPA, Helles, RIS
Lagering: Doppelbock, Wee Baby Seamus
Kegged: 4 am Dry Stout, Barleywine