As a background there is a context to this, a concept, and logical design.
Our findings show that a 12 server grid (Intel i7) with 500 Gb of RAM will process everything in less than 5 minutes (for a population of 5.1 million), on a hardware platform costing 5% of todays expenses. We also see that having full test-coverage is highly achievable and will of course drastic reduce maintenance cost in the long run. Plain Java with good class names and methods (DSL "Domain Specific Language") makes this rock.
This platform handle tax forms at over 50.000 forms pr. second.
The aggregates (as defined in Domain Driven Design) really make the difference, and in this domain it is a great fit.
BTW: using this type of in memory architecture will also gain applications who do not need scale. Storage is asynchronous from the usage scenarios. Just store when the right business state is met. The business logic and information model is nice and clean. No persistence tweaking anymore :-)
See you at SW2012!