We bought this as a "Christmas present" for our two cats to replace the small one we built for them in late 2009 -- they had absolutely demolished the sisal rope wrapped around the posts.  They love it and spend a great deal of time sleeping on one of the platforms, trying to "kill" the hanging toys, or chasing one another all over it.

The only complaint we have is that the lowest platform (not the house) snapped along a fault line or something with all of the jumping and bouncing the cats were doing on it.  We ended up removing it and just screwing the posts together.  The cats just climb right up the posts or get their stretch on.