all via css3 transitions. 

This scroll effect is not annoying because you always feel in control. Unlike the apple scroll effects, as a user you’re not merely beginning the animation, you control the entire pace of it. For this reason it’s important for it to be continuous (as opposed to taking a continuous scroll wheel and mapping it to discretized steps, as with many sites).

The graphics also invite the user to make their screen bigger. Which is a cool side-effect as well.