I typically run ~37 lands. I have only been playing Magic for about a year. The couple decks that I have that are less than that have other ways of using mana. I
forget which video, but Mitch from Commander's Quarters once mentioned you should have somewhere around ~45 mana sources, so if you have 36 lands then you should have 9 other ways to get mana. I tend to think 45 is high, but it is a good way to go about thinking about it.
My group is typically a more casual group, although the more we play together the more others are tuning their decks, and we are getting higher and higher power level. I would say we probably only have 1-2 cEDH decks among the total collections of our group.
Someone can help me out with this, but I would say most of my decks are between a 6-8 power level. Personally, I wouldn't put any of mine in the 9 category; though these numbers are always subjective. If you are bored enough to go look, the descriptions should say whether they are in my collection or not.