I picked this up on cd last week (along with the firebird) after hearing it in a BSO concert; very good indeed. Odd storyline (prostitution rituals??) but what else can you expect from the "prog rocker" of classical music. Now I can see how influential he was to Yes , with such an interest in these odd time signatures and cross-rhythms. People say Gates could have been written by Stravinsky, what a ballet that would have been!
It also appears that Yes stole a line from this suite in The Prophet.