My son (possible CF) takes Singulair and has been for almost a year now. It does help alot with his asthma and allergies. He takes it along with asmanex (for airway control)and allegra (for sinus drip) plus his albuterol inhaler is as needed.
Price wise, we have BC/BS of NY and its a midline copay ($20). To the best of my knowledge, there isn't a generic form so that rules out walmarts $4 price.