H.L.
I will second the wrap/sling suggestion. Especially now that it is getting cold - you can keep your little one nice and snug and who wants to haul around a stroller anyway? : ) I use the Ergo now that my son is 5 months old. He faces in and will sleep in it when we walk. Used it with my older son until he was 2 or so - they last a long time in them. Easy to put on, etc.
Otherwise, I just have the car seat with the stroller attachment.