Comment 3 for bug 1077054

I've also noticed that if you have "Dim screen to save power" enabled it can be confusing in the following way:

Slider is 2/3 the way up, brightness is 175. The screen goes idle, brightness drops to 70. You grab the slider to lower the brightness. Concurrently with you sliding the slider lower, the Idle dim disables, so the first thing you see as you lower the slider is brightness going from 70 to 175, then slowly down as you slide, 170, 165, 160, etc. This looks strange.

The issue still occurs for me in the following way, even with "Dim screen to save power" disabled:

Start with the brightness fairly high, slide the bar to the right, lowering the brightness. When it gets to about 25, start sliding back up. The brightness will momentarily go to 20 before increasing.

Here's an example
22
22
22
22
22
22 <- start sliding up
20
20
20
20
28
28
28
35
35
35

I can still repro the issue using a mouse, so it's not just a touch issue.