Update – In response to queries regarding the technicalities of the post, we’d like to clarify what we’ve released here. We provided build instructions based on the AOSP project under the branch android-m-preview, showing the Android M platform changes so far. That build gives an early preview of Android M for custom ROM developers to play with. Be aware that at this point the API levels are still at Lollipop MR1, what we show is Android M Developer Preview purely from a platform perspective.
Note that the Android M Developer Preview for Nexus devices from Google supports the latest API level. Xperia devices flashed using the build instructions linked from this post, do not support those APIs.