No superpowers. I'm using it because M&M can also be used as a (in my opinion) nice generic level-less roleplaying system.
That said, it's almost level-less. Also the characters are humans, ordinary humans with potential to become more. No supermutants, deathclaws or ghoul PC's allowed, but I am working on some specific rules to use. As there are great diversities between the technologies of this setting.
There are roughly three levels of technology available. I am working on creating a few sample "packages" for origins of characters which roughly come down to: Primitive, Standard, Advanced for tech levels, and Clan, Democracy, Dictatorship for societal levels, and three lifestyles: Settled, Semi-Nomidic and Nomadic.
Those packages will either serve as examples or they are obligatory for your character's background. More specific details I am still thinking about.