Okay ladies, give me all of the advice!

I have decided that I do not want to carry around a carseat carrier. They are big, clunky, and not good for baby to spend a lot of time in. I think that I would much rather baby wear instead of carry the carseat (luckily I will have a late spring baby so that is possible weather wise).

My sister gave me her Chicco Keyfit 30 infant carrier that my nephew outgrew. Would it work to use that and just take the baby in and out leaving the seat in the car, or would I be better off purchasing a convertible seat?

Are there other tips you guys have for not using an infant carrier?

This seems like a radical idea in my community but I have been dreading toting around that bulky infant carrier!