I'd say about 35lbs is what you could comfortably carry in a sling - traditional carriers truly are all-purpose! I love them so much!
Don't be afraid to experiment if what you have doesn't seem to be working for you. I had a sling I didn't like when my oldest daughter was born, and had to find one I liked better. Did a bit with the pouch with my younger daughter, but mostly used a ring sling of my own design for her and my younger son. But with the newest baby, I discovered wraps and MT's and I don't think I'll go back to one-shouldered carriers anytime soon!
The nice thing about a sling, though, is that it's VERY easy to learn how to use. There's no wrapping or tying involved - just throw it over your shoulder and pop the baby in! Makes errand-running a breeze ![Big Smile [:D]](../../emoticons/emotion-2.gif)
Stell - mama of 5 (for now)