i'm not sure wether it matters since it is related to the VS 2013 Roslyn Preview but just in case here's an error i encountered in beta2 with the following setup:
Windows 8.1 Pro x64 with media center (Core i5 4670K, 8GB DDR3, Radeon R9 270x).
I have installed:
Visual Studio 2012 Premium Update 4,
Visual Studio 2013 Ultimate Update 4 (with Roslyn Preview),
Visual Studio 2015 Ultimate Preview.
Since the VS 2015 Preview isn't supported yet i couldn't test wether this issue persists with the new compilers.
By the way, is there anything you can share about future VS support?
I have attached the project when it was compiled with the roslyn preview and both the generated js without roslyn and with roslyn.