The cats really like these cat trees and so I'm happy with them also.  I bought two of them for four cats of various sizes from 9 or 10 lbs. to 12 lbs. and two kittens (about 6 lbs.) and they seem to suit them all just fine.  Everybody wants on them a lot, so I may have to get another one. They are sturdy and the bases are a nice size so they don't tip over when the cats get rowdy. It helps when you introduce the trees if you sprinkle a little catnip on the carpeted surfaces.  I use a lightweight hand vac on them once a week and add fresh catnip.
I looked long and hard before settling on these, and it was worth it.  The price is very good compared to similar products, and it was great that they came fully assembled. The cats love the big boxes as well;  I cut holes in them and they play for hours. We've had these for about two months and so far they are showing little or no wear.