Those using DD4T in a Tridion 2013 SP1 environment may find that the Content Delivery assemblies referenced by the latest DD4T Tridion providers aren't fully compatible with the latest Tridion JAR files. I had issues, in particular, when setting up Session Preview for Experience Manager.
This can be remedied simply by recompiling the Tridion 2013 DD4T providers with references to the latest Content Delivery DLLs. Hopefully, this will soon be properly integrated with the framework as an additional provider option. In the meantime, however, here's a NuGet package for a build with the Tridion 2013 SP1 assemblies.
PM> Install-Package DD4T-Tridion-2013sp1
Install this package, ensure you're using the Tridion 2013 DD4T providers in your IoC container and you're all set. Note that, once the 2013 SP1 providers are officially added to the DD4T framework, there will probably be a distinct
DD4T.Providers.SDLTridion2013sp1 assembly but, for now, we'll just impersonate the default 2013 assembly to avoid having to recompile the whole framework and add support for a new provider version.
Drop a note in the comments if you have any trouble getting up and running.