Old question, but take a look at Mapster. It's a lot faster than AutoMapper (5-10X in the scenarios I've used it in) if performance is critical and supports most AutoMapper scenarios. Always remember to perf test as results vary by scenario.
We've dropped a new 3.x version that works for .Net 4.0/4.5/Core, supports several new features, and has big perf improvements.
http://www.nuget.org/packages/Mapster/
https://github.com/eswann/Mapster
Disclosure...it's one of my projects that was created for a high load service where AutoMapper started showing up as one of our bottlenecks.
