I've been using them since they first came out and I like them.
Let me add to the comments already posted:
Once you light it, it takes about 15-20 minutes for it to clear most of the bugs around you.
Also, it's less efficient when there's wind - but then the more wind there is, the less bugs there usually are.
Once in a while when an animal gets a whiff of it, there is some sort of a reaction - ranging from indifference, to curiosity, to not liking it and acting nervous, to being spooked.