It's definitely a must. That was my first (and only) XANADU experience, but the stoy was still told to me. Very fun show, ESPECIALLY from on stage. They are not assigned, so when you arrive, get there early and tell the on stage usher to sit you in the center.
The theatre is so small, on stage or in the audience - the only difference is perspective.
"The Spectacle has, indeed, an emotional attraction of its own, but, of all the parts, it is the least artistic, and connected least with the art of poetry. For the power of Tragedy, we may be sure, is felt even apart from representation and actors. Besides, the production of spectacular effects depends more on the art of the stage machinist than on that of the poet."
--Aristotle