We have 5 rescue cats.  All of them, except for the largest cat (14lbs.), loves this cat tree; the platforms are just a bit small for him to be comfortable. The rest of them took to it like ducks to water!  The only part that I would change is the very top piece. I think the landing under it needs to be wider for smaller cats to get down from the top.  Unbelievably, our one blind cat (all 6.5lbs of her) is the first and ONLY one that has climbed to the very top...all on her own and on a daily basis now!! She gets up there and sits with a very proud stance and look on her face.  She scares me a bit when she is trying to get down because she paws around looking for a platform to land on. Since the first landing is directly underneath with no overhang, she tends to "monkey down" and manages to find it.
Otherwise, they all take turns sleeping in the cubby holes and spend their time on it while I work in my home office.