Users of CyanogenMod 10 will likely remember when the ROM first received M-Series builds for various devices. Well, now CyanogenMod 10.1 has moved on to the next stage of development too, and it's making milestone builds available for a selection of devices.
If you own one of the popular Nexus devices or a Samsung Galaxy S3, as well as a few other supported handsets, then you can download and install the Milestone 1 update right now.
For those unfamiliar with the various build names, M-Series, also known as milestone builds, they are intended to be mostly stable and should be considered suitable for everyday use. Compare them with the nightly builds, which are fairly stable but require regular reversions in order to patch small bugs and add missing content. Even so, don't mistake the M1 updates for the quality expected in a final build.
Below is a list of all the devices receiving the milestone update:
The developers have also stated that CM10.1 is on track to be a stable release, so hopefully we'll be seeing a few more devices added to the M1 build list in the near future. You can find a list of all the supported devices and files for this update on the CyanogenMod download page.