It presumably derives from Nietzsche's Übermensch, which in English became known as Superman. (Was Shaw the first to use Superman in English, or were there translations of Nietzsche before him?) Freud then coined the term über-ich, Englished as super-ego.

The use of über in English seems to me to be a geeky or subculture thing: someone might be described as an über-geek or indeed an über-babe. (Members of one site I use include Uberfetus and Ubermeme.)