As good as Android is at being a malleable and flexible platform that users and developers alike can shape to their exacting standards, it can be difficult to stay up-to-date in the Android world. In a landscape where big name brands like Samsung and HTC put their own spin on top of the Android that Google creates, it makes updates difficult to roll out quickly. This is one of the main factors at play when someone moves on to a custom ROM, such as CyanogenMod or something built from the AOSP code, as updates often arrive much quicker and there's not as much extra software to deal with, either. As such, CyanogenMod has become one of the most popular aftermarket versions of Android out there, and version 13 brings compatible devices Android 6.0.1 Marshmallow - as well as all the special source from CyanogenMod themselves, too - and it's now available in its nightly form on a lot more devices.
These devices include the OnePlus 2, which will be a big deal for users, especially given the history of CyanogenMod with OnePlus fans. Other high-profile inclusions here are the Moto X Pure, the Sony Tablet Z which is a much older Android tablet from the Japanese brand. Elsewhere, we see the Oppo R5 and Oppo R5s join the party as well as the YU Yureka. This is an interesting bunch of devices, especially the YU Yureka which is a device from India that runs Cyanogen OS, the closed-source version of CyanogenMod. The two share most of their DNA, but Cyanogen OS is slightly different and less generic than CyanogenMod overall.
It's important to remember that these are nightly releases, which means that a new ROM of CM13 will become available for these devices every day - give or take - so while fixes might come quick, so too is the chance of further problems. These nightly releases are designed to get some code out there before it's final, and can be a good option for the CyanogenMod team to get some feedback and see how far away from a final release they are.