Comment 36 for bug 35223

I think, that there are some issues mixed!

To make it clear: The current brightness level is not saved at all on shut down.
The setting is read out of System -> Preferences -> Power Management -> "Set display brightness to:"
Please set this parameter to a value you like. On start up the brightness will always be as you set there.
If not, this is really a bug. So please open a new bug with detailed description of your laptop.

If you like, that the current brightness level at shutdown is remembered on startup, please set the importance to wishlist.

Someone explained a third issue: When laptop is idle it dims the brightness, when in active use again the brightness management is confused.
If this is your problem please search related bugs for this problem.