For the performers, or the audience? And it differs depending on whether it is a professional or amateur/hobby performance. The former, I would say the point is for the enjoyment of the audience as that is what they're paying ot see. The latter is for the enjoyment of the performers.
My follow-up question: If the purpose of the performance is the enjoyment of the audience, why not just pander to the audience at the cost the play's integrity? MacBeth would be awesome if they had lightsabers...
In so far as the audience is concerned, yes. However, there is a certain amount of professional pride that the performers have for their production, in which technical perfection is also required.
Also, I don't think "staying true to the original work" and "technical perfection" are the same thing. How well your actors perform MacBeth with lightsabers is independent from how accurately they reflect the original play. You can have a deviant performance that is technically excellent, or an "accurate" play that is performed poorly.
During his time, Shakespeare was pandering to the audience. And yes I agree. Macbeth would be awesome with lightsabers. Wait... Isn't that what Star Wars is already?
The enjoyment of the audience. Hands down. The technical execution can change from show to show, particularly in live theater. If it isn't an obvious mistake (I.E. Actors left in the black while in the middle of a line) then one moves on and leaves the audience unaware. That said, the glitter of the technical execution can make or break said audience's enjoyment.
I was considering this in reading various examples of throwing-it-in in film and theater. My kneejerk reaction would be to say that the enjoyment of the audience comes first, but then it occurred to me that, taken far enough, one can completely destroy the credibility and nature of a piece by changing it or improvising enough to make it more enjoyable to the audience.
It then occurred to me that one could easily argue that, in a performance, looking at it on the individual level, the purpose of performing is technical perfection -- one strives to perform ones role as best as possible, making no mistakes. Mistakes happen, sure, but the *ideal* is to enact your role flawlessly -- and if the performance and performers have inherent merit, that merit will shine brightest when executed perfectly. And in so shining, the audience will enjoy by default.
The truth is undoubtedly somewhere in the middle. I just wanted to spark a discussion.