What's the Big Deal with Hero Lab?
I use hero lab pretty heavily. For large and complicated systems (Pathfinder, GURPS etc.) getting the math and being able to see all your options in one place is very helpful for rapidly verifying/creating characters.
Hero Lab is also useful for games in flight as you can usually track resources like HP or magic pools or what not. For Pathfinder, for example, it tracks equipment, spells, XP, gold, encumbrance as well as auto-calculating your various stats due to spell effects or other modifiers like barbarian rage.