We went to three different performances in last year's season and my son (age 4 at the time) was thrilled with all three. They are nearly 2 hour performances, but he never lost interest.
The actors are professional and one of their performances last year earned a Best of Phoenix award for best production in all categories. I can't say enough about what a great resource this is for parents and kids.
The actors usually stay on stage afterward to answer questions and let kids explore the set. They also offer workshops for kids 5 and up where they actually put on a play at the end, but also learn about set and costume design.
This a really great organization and they put on fantastic productions.