I have two cats, one of which is a big ol' Tom named Raphael.  I didn't really think he would go to the top perch because he is a tad overweight (he's 11-years old).  He actually loves it and what's amazing is that it supports him, all 17+ pounds of him!   He loves being on the top perch and loves the little house in the bottom.  My other cats enjoys it too, but I expected her too.  :-)