On Day 2 of Mix 2011, it announced the new version of Silverlight.
The main features in this first beta version are:
- XAML Debugging with breakpoints for binding debugging
- Implicit data templates for easy UI reuse
- Double (and multi) click support
- GPU-accelerated XNA-compatible 3D and immediate-mode 2D API
- Low-latency sound effects and WAV support
- Real operating system windows and multi-display support
- Significant performance improvements, fixes and much more
You can see all necessary information and download links in http://www.silverlight.net/getstarted/silverlight-5-beta/