| I will usually only take a sleeping pill if I have taken my last bolus 4 or 5 hours before going to bed and my bg is stable. Since I am a pumper now, I have greater peace of mind with regards to sleeping since I have set a much lower basal rate at night.
What I've noticed with Ambien is that it works great, but you have a fairly small window. It does not "knock you out", but helps you fall asleep if you try. I find if I do not try to fall asleep within an hour of taking the pill, that it has loss it's effect and is pretty useless, YMMV. That may be why they have come out with Ambien CR (continual release).
Going low at night is no fun and I completely understand your frustration. I have been there way too many times myself. Moving to the pump was the best decision of my life with regards to my diabetes. Before the pump I would have terrible lows at night and I had to move my Lantus injections to from bedtime to morning and it did help. | 
