Comment # 55 on bug 1126480 from Andres Nogueiras

I just run through similar issues with my laptop during the last month, as I
moved from 15.0 to 15.1

The first symptom is that at boot it takes longer than the previous
distribution, due to nouveau driver trowing messages.

Then, once the X session starts, if wanted to change to a console, it takes
around 15 or 20 seconds. Going back to X is fast.

And when leaving the X session (closing) it hangs and do not let me switch to
tty.

I have to remotely log in, and the only thing I can do is poweroff the laptop.
For this takes around 5 to 10 minutes.