Gee, I guess I'm one of the lucky few. I've been an insomniac since childhood and Ambien really helps me. I started at 10 mg last Sept. I mentioned to my p-doc that I could tell when it wore off b/c I woke up after 6 hours. I wasn't complaining- I was getting more sleep than I ever had in my life. But he upped the dose to 12.5 mg Ambien CR. I sleep a full 8 hrs with it, but it is very expensive. Recently it has been less effective. Sometimes it takes me well over an hour to fall asleep, but then I stay asleep all night. I try not to take it every night b/c I'm worried about developing a tolerance to it. When I don't take it though, I'm awake most of the night. I hope it keeps working; I actually have a pretty normal energy level now. Keeping my fingers crossed.