We tried out a number of backpacks but couldn't find one that was comfortable for both us and our dog. 

The Kurgo one is awesome! Our 14lb dog enjoys riding in it and all of the various adjustment points means we can make it comfortable for us to wear. 
It is heavy, but that's what you'd expect having a dog strapped to your back!

Our dog has very short legs and a long body. We inserted several folded towels in order to make a booster seat for him. He now sits up nice and high. Before we created the booster, he was sitting too low in the bag and would start coughing from the zippered opening digging into his neck. 

I highly suggest playing around with boosting your dog if they have a more unusual body shape, especially short legs. 

We are so happy with this bag. We can take him on hikes and now that he's older he honestly seems to prefer getting to ride in the pack. He really loves it!