I played the Appassionata this year... the first movement took me MUCH longer to get around than the third movement. In Movement 3, the technique is laid out in front of you by page 2. I found the form, and the relentless ferocity of it kind of geared me up from the get go. The first movement has so many sudden "oh crap!" moments... like the first cascading diminished passage in the right hand... it's as 'out in the open' as a little Mozart Sonata. It's just silence, then WHOOOSH! If you stumble there, people will hear it. Also, in the recap, when the left hand has the triplet beat going, and the RH takes over the entire theme in octaves, it's difficult not to make that sound clunky, and execute all the trills musically, while the left hand almost makes you feel like you have to rush it.
I just found the first movement of the Appassionata was littered with these pitfalls and traps that can just snag you if you aren't relaxed or don't like your fingering. The third movement was very difficult, but as I said, it's all laid out from the beginning. Movement one has so many moments where it 'one ups' itself technically, and it is a very long movement..
One of my friends played the Waldstein in her second year, and she's an incredible pianist... her only description of the piece was "it's serene"... so I doubt she even noticed if it was hard haha. Like I said in the thread about Chopin's 3rd Ballade Vs. the Barcarolle: if you can play one intelligently and with a good musical sense, you probably have a good shot at the other.