For a while I was really hooked on the Febreeze air spray but I found that I didn't like the idea of spray being spritzed around all the time and landing on my furnishings, most of which have some form of glass on them. I noticed little dots of left over spray on occasion so decided to purchase the plug-ins again.
The one I purchased was Morning Walk, Meadow Rain - a dual oil plug-in that sits almost unnoticed except for the really nice smell it emits. This plug in is set to last up to 60 days which I really like and so far I am on about day 20 and the house still smells great.
The plug-in emits a small release of scent every few minutes from the dual chamber glass container that snaps into place on the plastic plug in. Once put into an outlet, a small green light turns on to let you know power is being sourced through the plug in and perhaps 60 seconds after plugging it in, you begin to smell the scent. Every few minutes one scent will be emitted and a few minutes later the other scent. The two go together quite nicely and I haven't noticed any odd scent being created because of this dual aromatherapy.
It isn't overpowering - very subtle actually but there is a noticable difference that doesn't smell perfumey or too strong. I purchased one for the main floor and in a matter of about 20 minutes the entire downstairs area smelled great and had started to waft up to the 2nd floor. Bonus.
I like the plug in concept as I simply plug it into the outlet and forget about it. The cost isn't bad although I have seen these units selling for over $13 - I don't think I'd go that far, but for $5.99 it was well worth the money and I'd purchase more of these.