My preparation paid off - I got an idea of some German musical terms ahead of time so I was less surprised when the conductor would seem to change the tempo in almost every bar in the first movement, etc. Because I wasn't hunched over my part trying to read and define terms, I got to sit back and enjoy what was going on around me - for instance, some beautiful contrapuntal woodwind choir parts in the third and fourth movements, glorious bass trombone and horn solos, and the interweaving of interesting percussion parts.
I will be the first to admit that I attempted to play probably about 75% of the notes on the page, and played probably about 75% of those correctly, but I didn't once lose my place! I'm happy to say that I could at least confidently watch the notes go by until I reached a place I had prepared more adequately. I seemed to fit in in this respect, excluding of course principal chairs of sections, who were fantastically talented and very hard workers.
Our conductor was likewise very talented and extremely well-prepared (I don't think conductors are allowed to sightread the same way instrumentalists are). Of course, in a professional setting, it is EXPECTED that each individual prepare his or her part adequately before rehearsal; I would have been expected to be able to play any note at near-tempo at the first rehearsal with expert musicianship and sensitivity to my conductor's instructions. Thankfully, this time we were just expected to enjoy it as much as we could, and watch for tempo and meter changes.