I bought this for my over weight cat, hoping it would encourage him to be more active. It is sturdy, I have it up against a wall for extra stability. As my cat is almost 18 lbs, he hangs over the sides a bit, especially on top. He does fit in the house though.  He does like the sisal posts and plays with the toy. 

Pros: Easy to assemble
Cons: Platforms could be a little larger