Apparently from Joel Hewitt’s blog, the iPhone is lacking in some Javascript events. Namely mousemove and doubleclicking. And you get mousedown and mouseup at the same time, which is interesting.
This will mostly likely break current apps and make new apps significantly harder to develop.
So much for Steve Jobs’ promise that if you make your web app work with Safari on your computer it will work with the iPhone.
Update
I will hopefully soon have my own iPhone, but I’m also thinking that mouseover and mouseout events might not work either?