Visual Studio 2015 Preview SDK Working?

Steps to repro:

1. Install VS2015 Preview on Windows 8.1
2. Install VS2015 Preview SDK
3. Create a new extension project (Other Project Types | Extensibility | Visual Studio Package)
4. Take the defaults including generating unit tests
5. Run unit tests
6. LoadPackageTest test fails

Tried loading the package in /Exp. The package constructor is not called and the debug write messages do not appear in the output window.

Perhaps it's too early in the product cycle to write extensions?