in our experience the trick is to have the baby in the cot next to the bed with the side down....so that the cot is like an extension to the bed...and that the parent who can manage on less sleep, or is the lightest sleeps next to the cot....if the baby stirs pop the dummy back in quickly...we used them for all of our three....the trick is to get to them to soothe them before they wake up properly and thus, from the baby's point of view, their sleep is unbroken. The trick is to establish a routine....our first child slept through from 4 weeks, our second from two weeks and our third, we had it down to a tee by then, slept through on his first night home from hospital.
All I can say is that this worked for us.