I think this is a really cool idea – a Mac mini with dual HDDs (no optical drive) and a copy of Snow Leopard Server. If only they had 2.5″ HDDs bigger than 500GB.
I also think Apple should have dropped a few of the USB2.0 ports and added a second gigabit ethernet port (although that would have required a motherboard change, the second HDD just requires the internal adapter and case to be modified).
Still – very cool. If I only had the spare cash…