[sniskelsowwef]

Yes!

You save some extra battery power by manually adjusting brightness only when needed instead of having it analyse the ambient light and adjust at every moment.

My personal experience is that battery life improves as I often forgot to lower the battery life. I had it set to manual for a year or so. It wasn't a massive increase, maybe a couple of hours, but the convenience of not having to go into settings to change it all the time was worth it. Saying that, the SGS2 makes it very easy to change the display brightness so I might just stop moaning and do it myself.