I have been using Airwick for quite sometime. I have used other brands and I feel that they work about the same but Airwick is cheaper. I almost always use Spicy which smells like cinnimon because I think it is much stronger than the other scents available. I reccomend the oil because it seems to last longer than most of the gels plugin. Airwick only cost about $2.49 for refills. I usually go to my local Walmart, but you can find them at any store you go to.
Usually on any given month I have to replace mine about 30-35 days and the scent usually starts out real strong for the 2-3 days and starts to taper off so that it is lightly noticable. There are several scents that are offered like Citrus, Floral, Fresh, Vanilla, Lavander, as well as several others.
Airwick also makes other great products that I find very useful as well like the Stick Ups and Nightlight Oils. I would reccomend it to anyone looking to change from the other competiters or looking for a change in scents. I think that you will be very happy with what they have to offer while making your home or office smell welcoming.