I was in Phoenix for work one weekend. I had to be in town for Thursday and again Monday, enough time that it wasn't worth it (for me) to go to an airport and turn around a short time later.
The Botanical garden kept popping up as a top place to visit. When I was there the Cithuly exhibit was going on. Knowing it would be lit up for night I arrived later in the day, did a circuit, took a nap in my car, then came back and did another circuit of the exhibits lit up.
They have a great variety of desert and arid plants. Most Botanical Gardens I've gone to have a much different climate with plants that are used to water and it was very interesting to see the difference of the desert plants. For me, it was enhanced by the art among the plants, although I did spend a lot less time reading the signs or learning about the plants than I would have otherwise. If there hadn't been the art I'm not sure my rating, but no less than a four.