I have tried the Kelty backpack-style, and my son was way too big and felt unstable in there. Then a Kelty top-of-the-line Adventurer. Son was comfortable but I was not comfortable no matter what adjustments I made. I am around 5' 11 light weight medium frame. The Kelty was also so big & bulky and was a pain to fold down. And the auto-kick-stand never worked right, and was annoying because it swung out when there kid wasn't in the pack. Next we tried a Phil & Ted's Metro carrier. Nice and small, but uncomfortable for me. This one remains to be sold.

When I first tried a Deuter, I knew I found the right one. This one is significantly more comfortable than the others. It has the right balance of size - comfort - weight. The adjustments are well thought out. It is super comfortable and does a great job distributing the weight properly. The entrance and exit is much improved over the kelty, a huge plus. My son (20 months) love to buckle the buckles himself. The 7-point harness is ingenious, comfortable, secure, and easy to buckle once you get used to it. There is adequate room in the pack, with several closed and open pockets. I even used the "hydration pack compartment" to store flat things, like magazines.

The pack folds down/compacts very easily. We recently traveled internationally with it and no one minded us bringing it on board in addition to our carry-ons because I had it folded down. It is also very well made - the German engineering is apparent, even in the sturdy frame itself.

After all the other packs we used, this is the only one that I still look forward to, still find comfortable, and still use regularly for hours at a time. My son weighs around 30 lbs and I think it will be no problem to keep carrying him around this way for at least another 10 lbs.

Another benefit is that the frame support allows my son to rest his legs on it. I suspect this helps prevent his legs from falling asleep due to lack of circulation.

We also purchased the sunroof/rain cover, rain cover, and neck cushion. The accessories are neat. We've only used the sunroof/rain cover so far and it worked just fine.