The first thing to note about the SDK is the new installer and the SDK manager. This new infrastructure will allow developers to receive updates to the SDK. My favorite feature is the diagnostics window. Most of my development uses cloud services. The new diagnostics window allows you to monitor the network traffic. This new feature already saved me a lot of time while using some REST services.
If you have a webcam on your developer desktop, you can now use it together with the SDK to test camera applications. Keep an eye on the diagnostics window while testing your camera application, you will notice instructions to press CTRL+W when your application needs to use the camera. You need to do this only once.
In addition to these new SDK features, there are the added tools for the new Series 40 features. SDK not only introduces the route editor for simulating location data but also provides additional support for cell-id based location inaccuracies.
Also introduced the in-App purchase simulator. Yes, Series 40 is about to get new APIs for supporting in-app purchase, but more about that later. The simulation tool is not yet complete on the beta release and is provided as an alpha level tool to get early adopters to get familiar with the tools and API.
I think even in its beta release SDK provides a good alternative Java ME emulator with some bells and whistles. So give it a try, provide some feedback to the team.