Latest snapshot of the WebSharper repositories (Bitbucket and at GitHub) showcases some build automation I finally managed to get working. It starts from MSBuild that uses NuGet to pull dependencies, including build dependencies, and then jumps to FAKE - using the alpha pre-release FAKE version has solved some F# version problems I faced earlier. It builds a lot of code, creates an output NuGet package, and also creates several Visual Studio templates that it packages up into a VSIX extensibility package - using the free to use API we are releasing under IntelliFactory.Build.
Things are looking a bit better since the build succeeds from scratch inside the AppHarbor environment that is currently hooked up - as a simple build server.
Despite the modest progress, build automation is still a nightmare. I think we need a much simpler story, one that would definitely involve the NuGet repository as a global binaries library and F# as the language for all build logic, with MSBuild in support role (generating MSBuild scripts for Visual Studio users).
See also the discussion on ScriptCS - this project attempts to do something very similar based on C#. I like their authors' emphasis on Node Package Manager as the model.
A thought that occurred to me frequently when debugging the builds was the simple question - why do all the parts have to work with process isolation barriers? It seems like we are trying to play the UNIX game on Windows, where the filesystem simply does not keep up, and processes have an unbearably slow cold start. For example, in principle, why invoke NuGet or MSBuild for that matter as a process through the command line, when there is .NET API for both? It seems that PowerShell at least allows Cmdlet's to keep some state in-memory, so reusing the same Cmdlet is vastly faster than invoking the same functionality in a separate process. I might be working on the tool along these lines as time permits.
A big win would be to have sane F# compiler (without the famous toxic nuclear waste that Haskell avoids by controlling side effects in the type system).. Then we would not have to invoke it in a separate process for each project in the solution. This could drastically reduce build times.