Does anyone commit to one of these extremes, or are you like me and barely ever touch it?
Maybe if I happen to be low on health and it's night I'll slide it over once and then back to neutral later, but it isn't really a major decision as it doesn't affect how I play my character. I think the general concept of it is very neat, in that you could have some bonuses depending on whether it is night or day, but the health regen feels a bit too weak of a bonus to me.
Maybe a perception increase during the day, with a decrease at night (or vice versa), would enable people to specialize at hunting and foraging in either night or day. Or perhaps an increase/decrease in stamina consumption, so you can get more work done or run away/chase people down better (or even swim if that's your thing). I'd like to see this slider matter more than it does now, and make me care about whether it is day or night (if I choose to, of course).