Acropolis is a great project!! This is what I can see after a bit of playing with the first bits...
The "Acropolis" scope is to help the developer to make modular, business focused, client .NET applications by using the last .NET technologies. Its target is ambitious because it covers one of the main requisites of a modern architecture: a Windows application must be modular and extensible, with a clear separation between business logic and UI.
Composite UI Application Block (CAB) has made a great work on this field but Acropolis is a step in the future.
The "Acropolist project" seems to start with a clear target: makes the developer life more easy. And you can see this when you start writing an application.
After choosing an Acropolis project inside the Visual Studio environment, a nice wizard starts. You can choose the main theme for your application:
the Application Level Navigation:
and the main Application Window Layout (if you want a menu, a status bar, a toolbar etc.):
After these steps, your UI is done and the wizard makes a clear separation between UI and business logic. You can manually edit the generated XAML to customzie your UI as you want.
Inside the Acropolis Framework there are a set of components that you can use to start modeling your application. All are extensible.
As you can see by these first screenshots, making a modular application with Acropolis is quite simple, more simple that using CAB for example. The application skeleton is done with few steps and the productivity can increase a lot (a graphic expert can start working on the UI with XAML while the developers can work with the main business logic).
If you have a team of developers, start thinking about introducing Acropolis: the advantages of its adoption are really a lot.
I'm really fascinating about this project... I'm sure it will give me lots of satisfactions soon... 
P.S. a Ribbon UI control (maybe integrated with the Wizard) will be possible?