I sometimes get quite odd behaviour with the dimmer. Sometimes it's much dimmer than it ought to be (a reboot often fixes this, but turning the lights on and off doesn't). It seemed to be much more common with beta3 than beta7, but it still happens occasionally.

I got it last night, but didn't check whether I get the same non-linear response to the adjustment that happened with beta3. (e.g. 30% much brighter than 40%).

Is the dimmer hardware-controlled, or software? Could it be interacting with the greyscale stuff in some way?