Have your doubts about the tiled interface in Windows 8? Well, if this kid is any indication, it's not hard to get the hang of. With some commands from his dad, and a little (sometimes a little annoying) guidance here and there, he's able to get around just fine, and he's only three years old.
Of course, the biggest advantage this kid has is probably learning his way around effectively from scratch. Grandma would be likely to have a bit more trouble with the change not because of the new interface itself, but rather because she's used to the old one. But that also goes for just about any change. Only time will tell how the world at large cozies up to the whole Start Screen thing.
Chances are we're soon going to see a whole army (generation) of kids like these, who can't even fathom why we ever had a weird pop up list thing in the first place. Welcome to the future, where you always feel old. [Reddit]