Don't get me wrong - I love babywearing. We would have bought a (non-broken) stroller long ago if I didn't. But there are advantages and disadvantages to any way of doing things, so I thought I'd lay out the pros and cons for anyone trying to decide on an Ergo vs a Peg Perego.
Pro: Never have to wrestle a stroller in and out of the car. Both of my carriers fit in the diaper bag (the sling better than the mei tai).
Con: Occasionally have to wrestle with the mei tai straps. They're long and there's just no good way to store them and get them in and out quickly. This is why I use the sling if I'll be making lots of stops.
Pro: Never have to drive a stroller through too-small aisles.
Con: It's much like being pregnant, in that sometimes you've got to squeeze yourself a bit. Also, nowhere to hang a diaper bag, so if you've got a huge one that adds heft. I recommend a small diaper bag or backpack to go with a carrier.
Pro: You can take the baby out and not be left trying to wrangle both a baby and an empty stroller.
Con: You look a little silly with an empty carrier hanging off you. At least with the sling I just look like a girl scout (my sling is solid khaki); we joke about the mei tai being my flak jacket. Also, no empty stroller to carry other things in.
Pro: If, like me, you're having trouble scheduling workouts post-baby, a good hour long shopping trip while wearing 10+ lbs of baby definitely counts as exercise! And with the mei tai, it's quite comfortable exercise, easy on the back.
Con: If you're really tired, it's still a workout.
Pro: Baby is right there, always kissable and it's easy to monitor where little hands are reaching.
Con: They might be reaching for your face or hair, though not too often because the rest of the world is so interesting.
Pro: It's possible (even easy for some people in the right carrier) to nurse while walking/hiking/shopping/etc.
Con: Once the baby knows this is an option, if they're hungry they may not take "later" for an answer. I usually have to turn him so he's facing out when he gets insistent at the wrong time.
Overall, for me the good outweighs the bad. For many, having both a stroller and a carrier available is best. And I'm sure there are some people that just weren't meant for babywearing. Good luck figuring out which is best for you!