Picked this up so I could take my 65lb Golden Retriever into the woods with me. His ability to carry all of his own gear was great! The pack adjusts well, rides well and didn't seem to overburden fido. You do have to distribute evenly and the front harness gives he dog a lot more leverage if you attach the leash to the pack directly. Lots of neat features to go along with the simple saddle bag design. My dog doesn't like using the bathroom in the pack, but its not difficult to remove and put back on. He didn't mind wearing it the first time either.
My border collie uses a size s. We just hiked to the top of pyramid peak near tahoe yesterday. It is a 4 mile hike with 4100 ft of vertical gain. It was very useful for her to carry her own food, water, treats and even my headlamp. The handle on the back came in very handy on a steep hike like that. The pack is fairly weatherproof and very durable. The best of all is the way hotties react when they see a cute dog wearing it! I love it. Make sure you get the right size so that it doesn't move around too much.
I purchased the Ruffwear Approach pack for my miniature schnauzer about three years ago. Since then, it has been taken up 14ers, on backpacking trips, through rivers/streams, from sand dunes to snowy trails, and on many trips in town. The pack is still holding up in terms of its stitching, material, and overall condition.Pros:-very durable -puts weight over shoulders rather than on dog's back-easy to put on and take off-handle allows you to lift your dog-can be used in the field or around townCons:-front harness is just a little too big for my dogTo sum: this is a durable product that can easily handle all of the bumps, scrapes, and weather your dog can throw at it.