Just remember that inequality per se is not a bad thing. Capitalism seems to me to be the only way to get people out of poverty, which is, of course, what we want.
With regard to class mobility, can we say at what level it gets too extreme or conversely at what level it is just perfect? A country such as Albania has a lower Gini coefficient than the US but is much, much poorer, but as such has less income inequality. I don’t believe that social mobility is much better there (I happen to have a good friend that lives in Tirana).