The buttons set up a clear linear path between "reading our slides" and "requesting an intro", with gentle animations showing your progress on that path. It's a simple but powerful metaphor. For me, far from distracting from the message they are trying to convey, the extra attention that has been lavished all over this page sends great messages about the competence of the people involved. Clearly to some this is going to come off as gratuitous; as usual it comes to down to how well they have judged their audience.

That said, as actual navigation I didn't find the buttons very usable. It would have been nice if there was a visual clue somewhere that the left and right keyboard arrows work.