Ugh. I think it's beyond awful. Incredibly slow and in many environments (chrome-windows) effectively non-functional. I still haven't made it to the end because of how slow and unresponsive it is.
I personally went through slide by slide just to read the specs. The transitions aren't the fastest given they overrode scroll events in favor of framing and animation, but it was done so intentionally as a form of presentation.
If you don't already have a fast computer, you probably will never want a fast computer. Makes complete sense.