In Visual Studio 2015 RC, while I can step into async functions within a console app that is part of the solution (the startup solution), or else, from a Unit Test project also within the solution, when I step into functions located in a separate project that exists within the solution, it does not step into it (using F11 etc) but just completes (steps over) the function call.
So I have to go to that function code and set a break point there for it to step into it, but even then, further function calls within that function again don't step into, but require, again, further breakpoints set on them first. This could drive someone crazy quickly, I hope there is some fix for this?!
Update: I just opened the same solution in Visual Studio 2013, and it works perfectly. So this really appears to be an issue in VStudio 2015 (RC) alone.