We had a Dueter kid comfort that I used twice. It worked fine, but holds the kids up and away from my center of gravity, making the load seem twice as heavy. My sister turned us onto the ergo baby...waaaaay more comfy, lighter carrying, lighter weight.

I really wanted to like the heavy duty frame backpack better, and was totally skeptical of the ergo baby, but after walking 50 yards with it, I was sold! Dueter just got sold on eBay in "as new" condition!