I love them! I use them all the time - I always bring two of the blank tan/grey ones to a game, plus a bunch of others. The more generic ones are most useful; all the forest trail ones & the city streets are great. I've also had good use from the bandit fort, the Keep, and I've used the very nice Country Inn.
Sometimes scaling is odd, I used the Warehouse one on Tuesday but really it was ridiculously too big for anything but "Area 54". For the Ship one I cut the decks out with scissors to use them better. I'm planning to use the Pirate Island one soon for a big battle on the shore.