I tried the new build, wanted to revert due to 4 hours of battery life and really annoying bugs - like explorer freezing so that I can't do anything.
I initially tried to use Windows Rollback, which appears to be broken in this build and told me my system needed to be repaired. Ok, so then I tried to download the Windows installation media from Microsoft - Microsofts downloader kept telling me that there was not enough space for the download, when there was. Tried this on a few drives then decided to torrent it, made my bootable USB and... Win 10 wouldn't use it. Same error as the rollback.
After this, I tried to reset, and this got me back to 8.1 - was never sure what version of Windows the reset would take me to, but I then recovered from my 8.1 image.
So basically, this build almost locked me onto Win 10.