We bought a dog stroller, which helps for when he stops wanting to walk, or is too bad, but it's a pain to take when he does go the whole way (it's a cheap one that has many design flaws). I kind of wish I got the backpack, but I think he would have hated it and made it unusable.
Our dog seems to love it. If we get the backpack out and open it up, he will jump in on his own and curl up there. He does also love his crate and a carrier we got for flights, so he is used to it.
But as with anything, YMMV. Best to do whatever is comfortable for your dog.
Our dog really doesn't like going in the buggy, but it's actually the best way to keep him walking along instead of endlessly sniffing and truffling for tidbits to eat. We just ask him if he wants to get in the buggy and he start motoring. He'll last for a little while in there before he starts crying to get out, unless he's really cold or hurt. A backpack would be awesome, but it'd be like trying to stuff a squirrel in your pants.
