I was caught in a catch-22. I wanted to use the infant car seat on the stroller deal, then move to using the stroller, but I got my sisters stroller and never got the attachment to snap the car seat into the stroller, so I just carried him around in his infant car seat -- for a LONG TIME. Once DS outgrew his infant car seat and went to an older one, he was old enough to walk around, so that's what he did. He didn't use a stroller. He was never accustomed to one, and so when he was old enough to go into even an umbrella stroller, he hated them. He just wanted to walk. So, at a year old, he was walking everywhere. We totally bypassed the carrier & the stroller. It will be different with the next one, as I am going to buy a working stroller/car seat combo.
*I do have to add that even now, when he's 3, he falls asleep in his carseat and I just take the whole thing with me.

I often take him out of the car - in his carseat - after he's fallen asleep and carry the whole thing into his room. I lean it back onto his toddler bed just a little, so he's kind of reclined backwards, and put the couch cushion under the front end that's tipped up in the air, to wedge it so it's secure. Then I unclasp the closures on the carrier, take his arms out of the straps, take off his shoes and cover him with a blanket if needed. He's taken MANY a nap like that as of late!

Just a couple nights ago, I unbuckled the car seat, covered him with my coat, and carried him in his carseat through the rain into the grocery store. I put the whole carseat into the cart and did all my shopping with him asleep.