I have tested quite a bit on 8.1. However there are some things that might make it “look” like things are not working.
8.1 seems to take you to the login screen after a while. However, from what I have seen, the screen says “logged in” and clicking the left arrow image simply removes the login screen.
The boxstarter window will not appear on the “start screen” but it should actually be running and switching to the desktop will allow you to see it. It can take several seconds or even a minute
after a reboot for it to start.
Boxstarter turns off uac before reboot. It does this so that the UAC prompt will not appear when it first runs. It should turn it back on when done. I have discovered a way around this and will
be removing the disabling of UAC in a near future release.
Does this at all align with what you are seeing?