Side-scrolling would be even better. That's the mechanism that I use for normal cover flow interaction, and that's what I expected this to work with.

Of course, if you don't have an input device that makes it easy to side-scroll (like a mouse with a vertical-only wheel) this doesn't make a whole lot of sense. Buttons at the side, response to right/left arrow keys, or a horizontal scroll bar would make a good backup for users without a trackpad.

Clicking on the cards would also be a welcome mechanism, but I imagine it would be used to jump to a specific card, rather than to go through one-by-one.