M-Series :
It is a destination version compatible mobile devices to emphasize the overall quality of the system, and therefore there taking the user experience, of course, always consider changing nightly build but will be available every month, unlike nightlies that are every night.
As we already know, the nightlies build compiled daily can be very functional, as in other cases very unstable. Clearly, M-Series offers a point of stability where users can build with these versions say operational, until maturity or final called stable versions.
