Easyiest, i dont want to get on a rant here....but oh well....
This peice in its entirty, is as hard as hell. Sure it might not be comparable to say the hammerklavier, whichs length makes tough. Moonlight when played properly and flawsy is a very tough task. The speed and fury of this peice makes it very agitated, as the name PRESTO AGITATO indicates
Moonlight is ground breaking as it broke as sorts of rules of piano sonatas at the time. Normal piano sonata format fast - slow - fast, this is slow faster, fastest. Like the 5th Sympony this sonata put most of the wieght on the last movement. (Beethoven adds a contrabasson, 3 trombones, and a piccilo in the last movement.)
As to respond to this fellows question, there are a number of ways to tackle this issue, first you must take the metedome and throw it on like 30 bbm, pratice it in quaters, and work up to speed, it may take a little while but after many repitions it starts to flow. If you cant get the arpegio to sound fluent, you might want to pedal (I know some people are going to strangle me for saying that) a LITTLE, just at the time where your fingers in you right hand flip from 5 to 1.
Follow the fingerings in this piece it is very nessisary.
By the way if you dont do this already play it so that the first C sharp is hit with your pinky and the second with your thumb.