The fast ring has always been there for Windows 10 Insiders who want to get their hands on every new build, and be able to participate in Microsoft's beta testing process in a much more involved way. There have been people, however, who believe the fast ring isn't fast enough. After talking about this issue internally for some time, Microsoft has found the way that they want to proceed.
One of the things that I have heard many times from Insiders in the Fast ring is that they want to see a faster pace of build availability. We’ve been considering how we want to respond to this feedback, and in January we expect to pick up the pace.
In the Windows Experience blog, Gabe Aul put out a post where he addressed the issue. He acknowledged that many Windows Insiders aren't satisfied with how the fast ring is going and announced that Microsoft is going to be dealing with that problem by loosening the criteria for what gets accepted into the fast ring. Now, the criteria will be much closer to that used to determine what goes to their internal rings.
The builds we release to the Fast ring may include more bugs and other issues that could be slightly more painful for some people to live with.
Gabe said that this is going to be a trade-off and that it's going to result in more buggy experiences coming to the fast ring. At the end of the day, this just means that you're going to have to have a tougher time living with the newer builds if you want to contribute to the vanguard of Windows beta testing. If you don't want to deal with the bugs, then it's suggested you switch over to the slow ring for a more stable experience, but you won't get to play with newer builds as quickly. Or you can save yourself the trouble and watch our very own Zac go hands-on with these builds.