Hahaha, I can join the sling-cum-doing-small/big business group too.
I am definitely "bigger" than lovexuan but I can't manage my 15kg using a sling anymore, actually stopped the sling when she was about 12kgs...I gave up the manduca when she was 10kgs!
Bought the Manduca (since ppl raved about it) while I was in Europe, walked the whole morning with my 12 kgs, I gave up, pass to hubby, he carried for the other half a day, he also gave up (he's much bigger but not much stronger than me! hmph!), so we spent one whole day the next day hunting for a baby store in Berlin to buy a stroller!!
That's why I'm still researching for a carrier...but a friend just gave me her mothercare carrier, so I guess I might use that for #2....or just stick to using a stroller when they pass the 10kg mark!