My Mom and I have one in every room of the house. We love them. Air "cleaner" it's not however its wonderful for freshening. I don't put drops in I squirt the stuff in.
My Mom does what Rainbow says is a no no but it's worked for her for 15 years or so. She goes to Romancing The Stone in the Mall and buys oil for it. They are fine as long as you clean it very well so it doesn't build up. Her favorite scent is dragon's blood.
We have both Rainbow and Thermax versions of these. Both are great.
