Parent who has done it on a 77W sitting in 9L. We put her in and she slept for ~30 minutes only, I ended up doing the rest of the flight letting her sleep on me (reclined ~45 degrees).

On a recent flight I took a stroll with my active toddler (we were not in Polaris), but I did pass by 9A/9L and we did see a baby in there. This was during Christmas travel time so a lot of families, so I suppose someone did book 9A/9L.