We have 3 cats. The old one likes the lower level and the two younger cat like the upper levels.
Tree does shake when one of the cats jumps onto the top tier or jumps off. They don't appear to be concerned about it tipping over so I won't be either. 
This tree is not covered in a carpet like material, it is more like an thin fleece. It has held up so far and we have had tree for over 6 months. Fur does vacuum off fairly easily but collects in the corners of the top 2 tiers ( I loosen it up with my fingers)



Cons: My cat has not used the scratching post areas.