|Beethoven's Emperor Concerto, 1st mvt, difficult LH [look up measure #]|
Having talked to a few people, it sounds like the above really is a hard passage, exceeding the difficulty of Chopin's Revolutionary etude. So often, in Beethoven's piano music, he just sticks in a passage where the notes are just so awkward to play, at least by my standards. The most notable example is probably the descending octaves in the final movement of the Waldstein sonata. Just how do you play them?
But mostly, since Beethoven is a great pianist himself, they're not anything he didn't think pianists couldn't manage. They're just things that require some time to work out. Like these couple of other spots:
[1st mvt coda passage]
[3rd movement passage 6 against 2 in RH passage]
There are still plenty of difficult passages in this concerto, but the ones above are the ones I have the most trouble with.