Cyanogen 13 nightlies give seven Android devices a taste of Marshmallow
Cyanogen recommends that if you are currently rockin' the CM 12.1 YOG4P or CM 12.1 YOG7D releases, to continue with the Snapshot release channel instead of the going with the nightlies. The latter doesn't offer the same quality as the Snapshot versions do, and is less stable. Cyanogen says it hopes to have a Snapshot based on CyanogenMod 13 by January.
Cyanogen also suggests that if you've used any unofficial CM13 source code, you should wipe it before starting to get involved with the nightlies because of compatibility issues. And if you currently are using a 12.1 nightly and want to flash Cyanogen 13 without using "Wipe Data/Factory Reset" (known as a dirty flash), you must also update third party add-ons in the same pass. According to Cyanogen, this means "if you use Xposed, OpenGapps, etc. flash a Marshmallow compatible version of them immediately after your CM13 flash."
source: CyanogenMod via AndroidCentral