I bought the ergo and infant insert a week ago. Dd is 5 weeks old. I love it!
I would not use the infant insert for a summer bub though, would be way too hot. But great for this time of year, we're in Melbourne.
My Dh is a big man, tall and heavy, and I'm petite, we both have used the ergo with no problems. Really adjustable.
I love it, hth.