Now there has been a lot of speculation with RemoteFX with the latest 2012R2 release. RemoteFX is a set of different feature. One of these features is the socalled vGPU.
vGPU is a feature which allows us to share GPU hardware between virtual machines. Now one thing that is important for those that wish to use vGPU feature on RemoteFX with 2012 R2 is that it is ONLY supported on client OS, meaning that is only supports Windows 7/8/8.1 Enterprise editions running as a guest VM on a 2012 R2 Server. Meaning that you cannot run a RDSH server and use the vGPU feature.
Microsoft has made a list of different RemoteFX features and listed the compability matrix here –> http://blogs.msdn.com/b/rds/archive/2012/11/26/remotefx-features-for-windows-8-and-windows-server-2012.aspx
And also important to remember that you can only use RemoteFX adapters on a Generation 1 virtual machine (It is not available on Generation 2) You can read more about the configuration and setup here –>
Microsoft has also made a list of different GPUs which make a good candidate for RemoteFX vGPU
RemoteFX only supports DX h/w acceleration. OpenGL support is a feature under consideration. If you are interested in learning how much vRAM is added to VMs using RemoteFX you can read more about here –> http://blogs.msdn.com/b/rds/archive/2013/12/04/remotefx-vgpu-improvements-in-windows-server-2012-r2.aspx
If you are having some issues with performance make sure that you have the latest drivers from the GPU vendor.