I love this bag because it's not too heavy and I've tried several backpack/rolling convertible travelers, and this one actually fits my larger 24 lb mini-schnauzer comfortably. It's great for taking him for short rides on the subway, and then I wear it as a backpack outside when getting to/from the train, and can have my hands free to walk himPros: large opening, lighter than similar bags, saves $$ with public transport. The side pockets can act as additional vents as they open up to mesh, and the front pocket (which works well for doggie supplies) is attached such that you can open the bottom section of the bag behind the pocket and reach in to pet dog's tummy while he's still in the bag.Cons: Not as attractive as some bags, wheels not that sturdy and they don't have covering in case you roll it in rain but then want to wear as a backpack (which I've seen on the "PetGear" bags). I don't know how the mesh will hold up.The only real complaint that I have is there is a bar in the back connecting the wheels which makes the backpack less comfortable. This is not cheap but reasonable as all of these bags are in this price range.I didn't expect to like this bag so much because it doesn't look as sleek or high tech as others, but I returned all those heavier, less ventilated bags and this one I've kept!