Tried a little - works well.
The bottle is 8.5 ounces and is supposed to last for three months. I like that I can use as much or as little as I want at a time. I made my own diffuser with a bottle and some reeds and I poured a small amount into the bottom of the bottle. The fragrance was subtle and as I moved my homemade diffuser around the house I enjoyed the scent very much. It wasn't so overpowering that my husband complained but he did notice the nice smell.
Next time I will try a little more oil in the diffuser and see how long it lasts and how strong the fragrance is. The way I use the oil I think it will last longer than 3 months, so for me it is a good value at $16 (on Amazon or through greenleafgifts.com).
My only knock against this oil is that ordering online you cannot test the smell ahead of time. You are committed when you click "complete purchase". I knew I would like Spa Springs because I had a Spa Springs candle before I got the diffuser refill oil. I also really enjoy the Haven scent and will get it when my current bottle runs out.
One final thing: I have made a few purchases from Greenleaf and things always arrive Super-fast and well packaged so that nothing breaks/leaks. I also enjoy the free sachet they tuck into the box.