There are actually two betas going on.  One for the SDK and one for the Porting Kit.  If you aren't familiar with the product, the SDK is all you need to try out creating managed applications.  There is an emulator that will let you see how the Micro Framework works for creating applications.  This SDK can also be used with a nubmer of development boards as they provide firmware updates for the 4.0 release.  The Porting Kit is used for adapting the runtime to your hardare. 

 Version 4.0 includes support for the following features:

    • HTTP and HTTPs: An object model is now provided for handing both HTTP clients and servers, similar to the .NET Framework, with the new types System.Net.HttpWebRequest, System.Net.HttpWebResponse, and System.Net.HttpListener from assembly System.Http.dll
    • Multi-touch: Basic support for multi-touch events, such as moving two fingers on a touch screen, is now provided in the object model and the emulator. Gesture support has been redesigned to be faster and more flexible.
    • Versioning: Versioning has been implemented to strictly identify assemblies by the version number at build time and on the device, and eventually re-deploying missing assemblies. Side-by-side load and bind for types belonging to the same assemblies with a different version number is supported. Support has also been added for assembly naming which includes the version number.
    • Emulator support for SSL and HTTPS: The emulator now explicitly supports SSL and HTTPs emulation.
    • Native XML Parser: The XML parser has been moved to native code for better performance.
    • Native collections: The collection classes have been moved to native code for performance, and have been enriched with Queue and Stack types.
    • Time sync: Devices can use the new Time Sync API to sync the system time with a specified server's time, automatically or manually.
    • Arbitrary display size: A custom heap and allocation area is now provided to support bitmaps larger than 760KB.
    • Large buffers: A new type, Microsoft.SPOT.Hardware.LargeBuffer, is provided for allocating buffers larger than 760KB, which would not fit in the managed heap.  This type is located in assembly Microsoft.SPOT.Hardware.
    • Watchdog and Power Level control: The power level and the watchdog behavior can now be controlled from the managed application using types Microsoft.SPOT.Hardware.PowerState and Microsoft.SPOT.Hardware.Watchdog from assembly Microsoft.SPOT.Hardware.dll.
    • Thick pens and gradient fills: A richer graphic model is now provided for designing widgets and controls.
    • TinyCore performance improvements: TinyCore performance has been enhanced in the area of event dispatching and layout.
The 4.0 release is the first release for which we have included the source code.  In the beta release, this is done without license to redistribute.  With the RTM, we will be releasing the source with redistribution rights as defined by the license.  We will be building a community to accelerate the development of the product.  Look for more on that in the near future.
 
To get either of the beta's, please go to connect.microsoft.com and look up the program that is right for you.

Let us know if you have any questions.