My cats absolutely love love love this!  They are all over it.  The only downfall is it took them a bit to figure out how to maneuver to the top.  But now that they have learned.. they are up at the top most of the time.  

Pros: Plenty of room for multiple cats, easy to put together, tall enough for the cats to get away from the dogs.
Cons: If you have very active cats, like mine, the unit wobbles a little when they literally RUN up to the top.