After upgrading/downgrading between 4.7 and 4.8 a couple of times now, I've seen on both occasions that powerdevil behaves poorly in 4.8 initially, at least until I go into its settings, to set/verify things, and to essentially force the configuration to get saved once.  Then, it all seems to work smoothly.

Symptoms include:
no action lid close
screen blanking at odd times
screen brightness not working as expected