Getting caught up on several points -- sorry to be late, it's a crazy semester.
Barbara, I'm not quite the Rosenkavlier addict I once was, either. I still like it, the great scenes still send me, the orchestral writing still delights me. But I must admit that Strauss overwrote it, blew it up with too much (and too grandiose) music for the novelette-ish sort of story it is. Very unusually among the operas that I would call favorites, I do think it's better when shortened with cuts.
In many otherwise uncut productions and recordings of Cosė fan tutte, "Ah! lo veggio" is the only thing to go. The tenor has between 20 and 30 high B flats in it (the note that tenors like Pavarotti make such a big climax of), and he can't heave his way on and off them -- they happen in the middle of phrases, often as the beginning of a descending scale. It's very unusual to encounter the aria in a live performance: bravo to Polenzani. From being a reliable "house tenor" for the Met, he has developed into a rather special artist of top rank. Both his live CD with the Britten Michelangelo sonnets and his Liszt CD are exceptionally fine.
I don't necessarily trust William Mann's relaying of opera anecdotes, or his writing in general. There are a lot of stories about Ferrarese, and they don't all agree.