Microsoft have just released a new build of Windows 10 for Windows Insiders on the fast ring. Build 10166 is once again about fit and finish with no new features. On the Windows Blog announcing the new build is no mention of any major issues and I have found the last few builds have been pretty stable.
Also in the update Microsoft are testing out the Microsoft Wi-Fi app (replacing Skype Wifi) and if you are in the Seattle area you can test out the app (more details on the Windows blog).
I wonder how many more builds we will see before July 29th RTM?