We have two cats with distinct personalities, and both of them love this tree.  They've used it daily since Christmas.  I've dubbed the board under the top nest the "hunting ledge," since it's a fun place to hang out and bat around both toy mice at once.  They also love the condo, which has flexible sides so that the larger one is comfortable.  One of them loves the IQ box and lower nest as well.  

Pros: Easy assembly, comfy for cats, facilities for many different cat activities.
Cons: No real cons, but keep your eye on the screws during assembly.  Two of the sizes look similar.