The hardware is open, so you can put other programs on it as well, such as Gnuk http://www.fsij.org/doc-gnuk/, which is more or less like the OpenPGP smart card feature of a Yubikey.

As with a lot of OSHW products, they often don't make financial sense when compared to mass-market equivalents. But they have intangible advantages over them, not all of which everyone cares about.