As many others have said on this forum... Mozart is not so difficult compared to many other composers if you talk about the technical level... but many think playing Mozart right is the most difficult thing... and I encourage you to delve into his music, because its really fantastic and will make you a better pianist.
Things that are difficult in Mozart:
You have not so many notes to hide behind, very clean playing is expected...
You must be very calm in your rythm and phrasing, without getting dull.
There is a whole lot of things that are not in the notes... Mozart has moving accents and culminations that are not always intuitive. Other german music is often EIN zwei drei fur

(no pun intended)
But Mozart loved italian music.
You need a large knowledge to understand Mozarts works... My teacher says that to play good Mozart you must first understand his operas.
Different voices often act like different instruments of the orchestra. Getting the nice sound and continuity is difficult...
I believe that if you listen to Mozart operas you will recognize a lot of things in his sonatas... one example: Compare the flute playing of tamino in Zauberflöte with some themes in 10th sonata in C-major (K330) 1st movement...
In the second movement the initial 3 notes should sound like a violin stroking in 1 direction, therefore add a slight crescendo. In the 3rd movement the left hands initial notes represent cello, etc, etc