Our dr put both my girls on it about 6 months ago. She wanted to take them off Mucomyst and do HS instead. Both girls also do Pulmozyme. Initially I cooperated and bought the HS (most insurance companies will not pay for it yet). We used it but I could tell no difference after a couple of months. Neither of my girls ever cough anyway so I suppose there just isn't anything for them to cough up. So, last month when they ran out of HS, I just switched them back to the Mucomyst. I haven't told the dr yet. I am waiting till our next visit in a few weeks. Honestly, it was a struggle for me to pay for it for both the girls. It's not very expensive, but when you start adding all the prescription copays for the girls we are already around $400.00 on a good month (and that's just prescriptions copays, not dr visits or anything else), so the added cost is hard. If I saw a benefit, I'd do it, but there was no difference that I could tell.
Edited to add: I just re-read your question and wanted to add that yes, they still had to take the albuterol. It was mixed in with the HS.
Also, my girls are 7 & 11 (will be 12 next month).
Good Luck with whatever you decide to do.