I've been watching the launch of Gov.uk and there's lots of really interesting elements they've included in the design.
One of my favorites is their Gov.UK performance dashboard
Couple items I like:
1) Shows real recent overall web traffic and puts it in a context
2) Shows comparison traffic to other agency web sites - this compares against other flagship UK sites
3) Categories types of format use - for example this shows that people are using the quick answers features a lot but not as much on the smart answers format.
I'll be interested in seeing how they develop these metrics over time. To me, the flagship of government digital metrics is still CDC - but gov.uk's is nipping at their heels.