We just got one and I used it for the first time in public yesterday 
The kid (5 months) fussed a bit being put in, looked at the ceiling for a few minutes, and slept through the rest of our trip at BJ's. This from the child who won't sleep at home unless she's in her Amby. It was super comfortable too, my right shoulder started to hurt after an hour or so but I realized it was just from carrying my enormous purse full of junk 
We have the regular Ergo and I found that it gets kind of hot, but the Sport may be cooler. FWIW I tried on both a Beco and an Ergo before I made my final decision, both were comfortable for me but the Ergo was cheaper.
The kid (5 months) fussed a bit being put in, looked at the ceiling for a few minutes, and slept through the rest of our trip at BJ's. This from the child who won't sleep at home unless she's in her Amby. It was super comfortable too, my right shoulder started to hurt after an hour or so but I realized it was just from carrying my enormous purse full of junk We have the regular Ergo and I found that it gets kind of hot, but the Sport may be cooler. FWIW I tried on both a Beco and an Ergo before I made my final decision, both were comfortable for me but the Ergo was cheaper.
