My cat, Marcus Waliby, LOVES this backpack. He goes camping with me but constantly escapes from a harness so I haven't been able to let him out. He cries and cries for me if I'm visiting other campers. We tried the backpack this past weekend and he was thrilled! I could hear him purring. When we got back from hiking and visiting I put the back pack away. Later I heard commotion in the camper, I go in and he crawled back inside the backpack which you can see on the second picture.
One thing I think they need to do though is to put air holes in the top. Once he is bigger he will cover up the air holes. I bought a large. He's not a year old yet so he will outgrow it soon. I'm not sure if they have an extra large. If they do I will definitely buy another one! I just got it so I don't know yet how it will hold up but it's comfortable and lightweight.