At 1:30 am last night, Willem woke up vomitting up his dinner. He was on his back at the time. Peter, my husband, woke up quickly and turned him over on to his stomach. Willem was barely awake, or even aware that he was throwing up so he tried to go back to sleep. We wouldn't allow it because he was rubbing his face in the puddle of vomit. We then cleaned him up as best we could without totally stripping the sheets and bathing him.
I'm just glad that we were cosleeping with him because he was so quiet throughout the whole thing that if he had been sleeping in the other room, we would not have known until the next morning. Not only would it have been an awful, disgusting mess, there's a chance that he may have aspirated vomit either when he was on his back throwing up, or when he rolled over and rubbed his face in it.
I have never heard of this benefit of cosleeping, that we'd be able to quickly attend to our child in a scary situation like that, but I've learned that cosleeping in this case may have prevented a potentially dangerous situation.