I only had a small cat tree previously, which my girl used so much it qualified as derelict housing!  This time I thought I'd go big - and she is completely thrilled to pieces with it.  Every single day she is in it, hiding from me until I walk by when she'll reach out and grab me. She cautiously learned how to jump a little higher every day until she reached the top - from the floor!  She was thrilled with herself!  I'm really glad she's so happy.