I don't think I've ever been so suprised by anything computer software related.
I loved lego as a child and I still think its cool. I can't wait to play with lego again with my children (when I actually have children, that is).
I think its a highly creative toy and seeing what you can come up with is fun.
It's bloody expensive now, though, but this "Lego Factory" service is sure to inspire plenty of nostalgic adults to spend more money on lego.
EDIT: I forgot to mention what was the surprising bit. Enterprising hackers have hacked the software making it easier for people to choose bricks from sets based on the cost of those packages ("palettes") or something. And the surprising is Lego are actually quite happy about that and encourage others to come up with ideas to make their software more fun.