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: