As usual, Max Firtman did an excellet talk on mobile HTML5. Luckily for him, the space changes so much that he can give a talk on the same topic every year.
The slides and resources are good, so I just want to point out a few things.
If we take the convention that 1 second is a fast page load and 100ms is a fast interaction response, the latency of mobile devices is pretty terrible with 2G topping out around 1 second and even 4G topping out around 180ms. When you consider that the radio might be idle, this gets even worse.
He also covered a lot of things that are good practices. The one I liked the most was his investigation of responsive design. In my job, we have mostly written it off as sending too much data only to have it hidden. He went further and pointed out the conditionals for IE that will never be needed on mobile. The large images and tons of unused CSS just make it more absurd. I fully agree with his statements to focus on mobile and do it well.