Babies are designed to wake at night... if formula was artifically extending their natural sleeping patterns I'd be concerned... i've heard that sleeping too deep can be dangerous for babies.
Absolutely! I would be very wary of anything added to formula to create an artificial sleep pattern... that just freaks me out.

I'm expressing fulltime for AR & haven't noticed anything different WRT her sleeping patterns to the other three.
She is in a fairly rough pattern, waking once early in the morning. I think that is much more to do with her than what or how she is fed. DD1 was FFed, DS1 was FFed from 8 weeks & DS2 was Bfed for 14 mths...so far AR is the best sleeper of the lot!