Library is C++11 Components and is claimed to be highly usable and fast. In fact, their introduction page particularly focuses on the performance part of the library. Folly has been tested with gcc 4.6 on 64 bit installations.
I just downloaded the library for a quick look and it should be interesting to peek into the code.
You can also have a look here: https://github.com/facebook/folly/blob/master/folly/docs/Overview.md