I am not talking about mmap() vs write() here. That is just ordinary propaganda. There is a lot of powerful ideas at work there. The two that I know about:
That is neither new, nor interesting "engineering". Lots of software that needs significant customization uses the host programming language for configuration.
How is "we used an existing data structure and deliberately misrepresent this as some amazing discovery" an amazing feat of engineering? This supports the notion that varnish's biggest achievement is an amazing feat of marketing.
Regarding the .so configuration: can you show other examples? I find this technique fascinating, as it combines speed, expressiveness and actually ease of use.
About the alternative heap implementation: can you point out who else has described this aggregated-heap data structure? I don't even know if it has any name, but sure as hell it is a good idea.
1) Compiling config file into an .so object.
2) Using innovative priority queue (heap) implementation: http://queue.acm.org/detail.cfm?id=1814327
Varnish userbase is the best proof for its quality though.