Now that RIM has released the BlackBerry PlayBook OS 2.1 developer beta they are following up with the Native SDK. The new Native SDK (NDK) beta brings us to v2.1 of the SDK for Windows, Mac, and Linux. You can also download the 2.1 Beta simulator to test it out.
Check out the downloads on the Native SDK page. Kudos to the RIM teams for the on time as promised delivery of these updates.