In terms of materials and manufacture, these packs are really nice quality. They're pretty large since they're designed for backcountry hiking, so they may not be a good choice if you're looking for a weekend or day hike packs or something for your dog to carry on daily walks.
The biggest gripe I have with them is the fact that the front straps goe straight across the dog's neck. I prefer packs that have a Y-front attachment since those are more comfortable for the dog and don't interfere with normal movement, your dog's flat collar, etc.
I have one for Kodee and I love it. It's really well-made and nice-looking, although he's only worn it empty, so I can't say how it will be loaded. I like the size - I bought it mainly for day hiking, and I don't think it will be too big. I like the fact that it has 3 straps (one for chest, and two instead of one for the belly). Most packs had only 1 belly strap that I saw, and I like that you can adjust the fit better with 2 straps for the belly). This pack hasn't interfered w/Kodee's collar/leash.
Like I said, he's only worn it empty, as he's too young to carry a load. He was already used to wearing a vest, so he never pays attention to the backpack when it's on, so it seems comfortable. I've never used a pack w/the Y front, so I can't compare it to that.