A white paper was published on the MSDN site today describing a new feature of .NET Framework 3.0 (formerly WinFX) setup - the ability of a 3rd party setup wrapper to register for progress messages and send cancellation requests when running setup in silent mode. This is a feature that I have heard a lot of 3rd parties ask for in all previous versions of the .NET Framework, so it is really exciting to see that it has been implemented and is now ready for use in real deployment scenarios.
In previous versions of the .NET Framework, if a developer wanted to run .NET Framework setup in silent mode, they did not have any way of tracking progress during installation or allow the user safely cancel .NET Framework setup. This led to scenarios like the "fake" progress indicator that we implemented as part of Visual Studio setup to provide the semblance of progress to the user.
The features described in this white paper allow a 3rd party setup package to register a callback function that can be used to listen for .NET Framework 3.0 setup progress messages. This allows the other setup process to display a more accurate progress bar during download and installation when the .NET Framework 3.0 is launched in silent mode. In addition, it allows the other setup process to request that the .NET Framework 3.0 setup cancel and rollback.
If you are planning to include the .NET Framework 3.0 as a part of your setup package and launch it in silent mode, I strongly encourage you to take a look at this white paper and consider implementing a callback function to allow your setup to provide more accurate progress UI and cancellation UI to your users.