In reply to joeb:
A big framed carrier is great if you need the carrying capacity. But if it's just for walking the dog, you could try something like an Ergo (
http://www.ergobabycarrier.com/ )or other soft structured carrier (Connecta, Papatum, Angelpack LX, erm, I run out of examples there, but there are loads) - baby is right up against your back, and you could probably use it from 4 months if she's got reasonable head control. Much, much lighter, and I find it much more comfortable (but that's at least partly 'cos the Macpacs, etc, are basically on a man's frame).
Have a Littlelife Ultralite I'm about to eBay - email me if that's of any interest! (A "framed" carrier, but with no carrying capacity). I bought it for round the shops, but am now a complete convert to the Ergo!