I went with my cousin and her six year old son two years ago. Joey went in there with the "this is boring" attitude. Threatened to walk out (he actually walked away from us, staying in sight, and waited for us to follow, but when we didn't, he came back). He then sat there, complaining about how boring it was, until my cousin took him out of the theatre.
I'm sure some kids handle things like that better did Joey did, but remember it is an hour long, and it can be boring for kids. Is your son used to going to church, and hearing choir music? My friend took her five year old nephew to see it, and he loved it. He is used to behaving in church, and his parents are very strict with him at church.
If you do go, I'd have something to keep your son occupied in case he gets bored (I told my cousin to take her son's gameboy, which she had carried around all week, and she didn't take my advice, and she paid for it).
Karen