I thought the 3rd movement was easy after my long and hard struggle with mv 1 (the war is not over yet). Well ... at first. Technically it was not that difficult, although there are a few complicated turns ... but when it came to interpretation, it got worse. It is a difficult piece in the musical aspect, especially if you see it as this final part of a whole sonata and not just a standalone piece ... What does it say? How do you play it?
The 3rd movement of Moonlight is technically hard, at least to me, but maybe I will crack the code soon. But musically it is just a "free improvisation" over movement 1, Beethoven going loose over the keys so to speak. Maybe movement 2 is included too, I have not analyzed it very much yet. I think I should try it soon, but aim for a very slow tempo. (No, I'm not an idiot, of course you have to start in a slow tempo! But sometimes your goal is to speed up as quickly as possible, and sometimes you keep on playing slowly as an exercise. BTW try that with Chopin's etudes as well, they work fine in slow tempo too!)