Well it has failed to install for me. I get to restart now, and nothing happens - just reboots immediately and says in update history and says it has failed to install.
I am now in process of creating an iso to try again. If this works, it is not the downloaded files specifically are the issue but how UUP works once it has downloaded files. This strongly suggests returning to install.esd is the way forward.
Reading the posts here, MS should be hanging their head in shame,. If we as seasoned Insiders are experiencing so many difficulties in upgrading to 162881, then it clearly shows that UUP is not a robust delivery method.
I have just created a feedback to MS for users here to upvote if they wish
Feedback Hub - Windows Insider
cheers
C
EDIT - UUPTOISO failed at last hurdle :-(.
============================================================
Creating install.wim . . .
============================================================
Using LZX compression with 4 threads
Archiving file data: 7308 MiB of 7308 MiB (100%) done
ERROR: error writing to standard output: No error
Errors were reported during export.
Press any key to exit.