Dubois Meets Fugger, a Cute Flash Interface.

Hmm, I think they preload first, because loading on the fly would hurt the animations. Actually the site only took 10secs for me to load and the content is more then worth it. I've seen much much worse sites concerning loading time, even very pro ones.
You also have to look at the target audience here.
They are located in belgium, where as far as i know, the connections are really fast.
Keyboard navigation would be a nice feature, but fairly said, i haven't meet anyone yet who doesn't use his mouse surfing on the web.
They do use a flash check and the site is made for flashplayer7, which penetration is almost 100%.

It's cute, but this isn't what Flash navigation is supposed to be like.

There's no fallback. If you turn off plug-ins, then visit the site, you get nothing but a white window... not even an error saying it requires Flash, much less an alternate non-Flash version of the site.

There's no keyboard accessibility at all, so if you prefer a keyboard over a mouse (or if you're disabled and have no choice), you're SOL. Flash supports all kinds of accessibility options and keyboard navigation features, but this site doesn't use any of them.

The load time is terrible. Flash can load 'on the fly' as it's running movies, but this site doesn't use that feature... instead you have to sit there waiting for it for a full minute before you can do anything.

The UI is complex enough that they had to explain it in a few places. "Click on the skulls." In a good site, it should be obvious where to click without any hinting. (Not to say that all sites should look boring, just that it should be obvious which objects on the screen can be interacted with and which can't.)

There's no reason this website couldn't be equally as cute and add in those features I mentioned.