A year or so ago, I saw this video from Scandinavia exploring what baby sees in a stroller verses a carrier. I thought it was a great piece (and I'll be honest, it's WAY more professional than ours), but I heard many complaints that it needed English subtitles (although the mamas said there was nothing more interesting than greetings, weather, etc.). I also heard complaints that the rear-facing stroller didn't account for older children who could see more in for forward facing stroller.
Now, a study in 2008 found that away facing strollers were more stressful for babies than rear-facing ones. In the study, it was found that mom engaged with the baby less in the front facing stroller. I recall thinking, "I always talked to my oldest when I used a stroller" (I didn't successfully babywear until my second). I discovered when editing the video that the researchers were right... not because I was ignoring my daughter, but because I didn't realize she was pointing things out. She tries a couple of times and then gives up. But when she's on my back, we're able to have a conversation about what we see. The stroller video is particularly illuminating to me because I was trying to steer the stroller so that she could see interesting things, and yet the perspective is so different that what was water jets and a lazy river to me was just people's rear ends and fences to her.
I'm not going to say that no one should ever use a stroller. On this particular day with 3 small children of my own, plus a friend and her 2 little ones, we definitely found the stroller indispensable for carrying bags. The little ones also took turns riding in it from time to time. After our experiment though, I will always try to trade off which children get the mama's eye view. No one should be trapped in a stroller all day.