I know that some people have said that they do not think the scent produced with this stone is comparable to a candle heated burner, but I have always been very happy with it. I usually add the oils without any water, but both work equally well for me. Yes, the bowl is shallow and therefore cannot take much water, but I don't have a problem with that. Perhaps the oils do need replacing quicker than in a candle heated burner, but logic suggests that if the oils have vaporised, they must be in the air, consequently scenting the room... This does a fine job scenting every room in my house.
I may be biased, because I far prefer to keep this plugged in unattended to keeping a candle (even a nightlight) burning. I have a very inquisitive cat who is fascinated by flames! I also find that it's very convenient for travelling. I've even used this in the office! Everybody loved it, said the room open plan room smelled far better with my little gadget running. Again, not something which could be done with a candle heated burner - health and safety would have had kittens if I'd been burning candles in the office.
Highly recommended. I own three!