This was delivered less than an hour ago and it was super simple to assemble. I only made one small mistake. When you lay out your pieces make sure you set aside the shelf that has the extra hole for the spring loaded fur ball to put on the top level. My 13 week old kitten went straight to the top but really loves the puzzle box that has the jungle bell balls.

Pros: Easy to assemble, kitten interactive
Cons: Can't think of any at this time