It's a green leafy herb, with a mild, very slightly sweet-bitter taste. According to
http://www.penzeys.com , heat tends to destroy its flavor, so it's most commonly used in cold dishes.
I have a bottle at home. I don't use it too often, but it is nice for a variation.
If you can't find it near you at a natural foods market, Penzey's (as mentioned before) is a great place to get your spices. I've never been disappointed.