Before the CyanogenMod team starts shifting its focus on Android 4.4 KitKat, it has decided to start roll out the first Milestone build of CM10.2, based on Android 4.3 Jelly Bean.
The M1 build is just the CM’s way of branding a build for each device as a bug-free extremely stable daily driver level. However, since this is not the final CM10.2 based build, there might be some minor bugs lurking around, but nothing too serious to affect usability. If you have been running an older version of Cyanogen, like say CM10.1.3, you can safely flash this M1 build on top without the need to format your device.
Over the coming few weeks, the CyanogenMod team will be focusing on Android 4.4 KitKat so development for the CM10.2 branch will slow down a bit. However, as always, the CyanogenMod team will release a stable CM10.2 build for all its supported devices before completely jumping to the KitKat branch. The team will also provide more information on which all devices it will support with KitKat down the line.
Head over to get.cm to download the CM10.2 M1 build for your device.