This place is almost nauseatingly spectacular! I've been in the valley on and off for the past 9 or so years, and I had never been until the other day.
I have an issue with heat and the sun, so we went early in the morning, but it was still kind of wearing on me. May I recommend avoiding visiting during the late spring/summer months if you're like me. The Chihuly works were a nice touch to all this place had going on. And the butterfly exhibit was humid and cramp, but provided a lot of great photo opportunities and was entertaining. Everyone is reduced to a 5 year old when it comes to butterflies, in a good way.
Oh and you can definitely get a nice work out taking on some of the longer trails at this place, so wear comfortable walking shoes. I saw a great deal of other events and exhibits posted that the botanical gardens have to offer throughout the year, and I can totally see myself revisiting time and time again.