I've also been on both, having recently switched to generic when it became available earlier this year. Not too much of a difference as far as I could tell. Funny thing was, also tried
Ambien CR 12.5 early in the year and it was like the most useless thing to me...got me drowsy and warm and almost happy feeling but never put me to sleep unless I chewed it open first. Needless to say, told the doc and was put back on the cheaper (and I guess for me more effective) regular release form.