The motivation of pion is not to build yet another web server or web application framework, but to help provide basic HTTP(S) functionality to new or existing C++ applications. If you're working on a Boost C++ application and would just like to use HTTP to provide a simple user interface or interact with run-time data, then pion might be for you.
pion::net is a highly under-estimated very well designed HTTP library for C++. It also does support SPDY. If you are familiar with C++ and boost you can start development in very short time. I hope some day it gets the attention it deserves.