I wasn't familiar with it at all, so I did a little research on it. It sounds very promising. It was launched in England in 2001 and just released in the U.S. in May 2007. I know my allergist who treats my asthma and allergies has told me several times that England gets the best asthma/allergy medications way ahead of us, knowing that, I would certainly give it a try. From what I read, I wouldn't hesitate to try it.
My allergist also says they are allowed to treat asthma more aggressively in England then they are here.