"If your page scrolls, you should have some indication that your page scrolls."

That's my approach. I don't think scrollbars are entirely necessary (and in a slide-to-slide webpage like this, having a scrollbar wouldn't really work since it'd break the UI), but having some indicator that you can scroll is necessary. It doesn't necessarily have to be a scrollbar though. Having content peeking out from beneath the fold is often enough to let the user know, "Hey! There's stuff down here! Scroll and check it out!"

Does it scroll? It doesn't do anything for me (Opera), so I guess everything's broken.

Introducing a javascript requirement to scroll the page?! That's just plain rude.

Scroll bars can look ugly, but at the least they should have a graphical representation that the page is scrollable. I also completely missed the rest of the website.

I legitimately missed the rest of the page and dismissed it as totally broken until I read this comment. Hopefully that emphasizes how right lifeformed is.