Microsoft debuted the new Release Preview track as part of Windows 10 Mobile Preview Build 10586.107, an otherwise uneventful preview release that fixes a few bugs. Available for desktop and mobile builds, the Release Preview rounds out the Fast and Slow tracks that have made up the Windows 10 Insider program.
When you opt for the Fast Ring, you accept risks. Microsoft is increasing the pace of new builds, and new bugs will arise as a result. Microsoft is advising users that there will be "some risk" to their devices—the trade-off is an opportunity to receive new features first. The Slow Ring takes a more conservative approach, with "less risk" to devices.
In some ways, the Release Preview appears to be even more conservative than the Slow ring as far as risk goes. Gabe Aul, the corporate vice president of the Engineering Systems Team, described it as: "Best for Insiders who enjoy getting early access to updates for the Current Branch, Microsoft applications, and drivers, with minimal risk to their devices, and still want to provide feedback to make Windows devices great."
All three tracks, or rings, will be able to provide feedback to Microsoft, which is the whole point of the preview experience.
Microsoft named three bugs which 10586.107 fixes:
Why this matters: New builds introduce bugs, sometimes catastrophic ones. If you're testing a build on a secondary PC, a bug that kills its ability to print may be annoying but not one that stops you in your tracks. Testing a new build on your only activated smartphone, however, can be a real sacrifice. If Microsoft releases a build that impairs a phone's ability to send texts, that can be a deal-breaker that keeps users from opting in to the Insider track. An Insider ring with a bit less risk will attract more users and therefore be better for OS development.