(Also, am I the only one who remembers that the Ultimate line was once targeted towards younger readers? Did they just give up on that?)
The Bendis-written stuff generally was; the Millar-written stuff, from the start, clearly skewed older.
There's also always been a tension between the idea that this is supposed to be a place to explore classic concepts free of continuity and the tendency of writers in all titles to totally change stuff for experimental purposes or gimmicks.