Huge success
Within minutes of being put up the cats were settling into their baskets (in fact they were determined to hunt the feathers before it was even put together).
In the few days since they've been very comfortable sleeping in the tree, using different baskets, sometimes even sharing a basket. They're jumping between baskets and climbing the tree, it's staying stable and upright through all this.
On top of all that, it looks terrific, and people have been asking where we got it.