As with any new kernel branch, the first one is always marked as mainline, which means that it's not yet ready to be deployed in stable GNU/Linux distributions, but only in those that are currently in development, such as Ubuntu 16.10 (Yakkety Yak). The status of the new kernel series changes to stable as soon as the first point release is out. Therefore, Linux kernel 4.8.1 is now stable enough to be used by any Linux-based OS. We also reported the other day that Linus Torvalds apologized for the inclusion of a kernel bug in the Linux 4.8 release, which shouldn't have affected anyone because no stable distribution was using it. We told then that it's just a matter of time before Linux kernel 4.8.1 is out to fix that issue and let OS vendors ship the new Linux 4.8 kernel series in the stable repositories of their operating systems.