This is a really handy tool! I tend to "travel" around to GM a lot (Pathfinder Society organized play, so local gamedays at stores, cons, friends' houses and so on) and this is a terrific alternative to carting around cases of minis. Very, very worth the money, even at full price (I bought mine at a local game store).
I'd love it if I could buy modular add-ons (I needed eight goblins the other day, and the box ships with four), but the PDF is fine for this (if you're not absolutely lazy... which I am, sometimes) if you print & mount what you need.
(These would be great for a player of a master summoner, conjurer wizard, etc. as well.)
It's definitely up there with the flip mats and condition cards in terms of utility. I'm tempted to buy a second box, actually (to keep in the trunk of my car along with my "just in case" dice and battle mat.)