They put my daugther on it a few months ago. It did take a few weeks before she started coughing a little more (she's not much of a producer), but now she'll cough more during therapy or we try and make her cough. She also does this type of breathing exercise, which takes about 3 minutes, and that really helps.
About the Saline mixture, I just did a little research on that. Right now we buy the 10% sodium chloride in vials. We have to mix it with 6 cc's of sterile water. After that is mixed together, we have to pull out 5 cc's and that is what she nebs. I asked about the pre-mixed vials, because we do a lot of after school activities and travel quite frequently. So having them ready to use in those situations would be a lot easier and convenient, not to mention more sterile. I also will be getting them from Foundation Care, which is a compounding pharmacy. (I also didn't know what compounding pharmacy meant.) Since they will make whatever you want and what the doctor prescribes, insurance doesn't cover it. They told me it costs about $.60 per vial. So if we got a 30 month supply, it would cost us $18.00. I'm going to give it a try, because we only would use them approx 2 times a week.
The other way, our insurance does cover it and since we use the saline with every therapy (3-4 times a day) we will do it this way. But I don't mind paying the extra when it's a convenience and it's rare.
Hope this helps!