I love Ambien. I take 1/2 of a 10mg pill every night. Just like you, I take hours to fall asleep.
It gives me no side effects, either. When I take 5mgs I don't necessarily feel sleepy if I'm up doing things but once I go to bed I fall asleep quickly.
Ten mgs is where it can get a bit wonky for me. One evening I took 10mgs and then DH and I watched a new episode of Desperate Housewives. The next day I asked him if he remembered to tape the show because I wanted to see it. I had absolutely no recall of having sat there, watched the show and discussed it with him.
I also asked the children, "Where did the leftover pizza go?". Apparently I ate it while watching Desperate Housewives.
That's when I started cutting the pills in half.
Have you tried taking one and going right to bed, even if you don't feel sleepy? If so, do you fall asleep or are you still staying awake for a long while?
I can't say if Ambien is connected with depression. I was taking Zoloft and now it's Wellbutrin for postpartum depression. For me, sleep deprivation is a major factor in depression, so Ambien may help with that.
Good luck to you! I really feel for you.