I'm really excited about Marvel making a more diverse choice for the flagship book of its Ultimate line. This is a great opportunity to bring in a wider spectrum of young readers, as Miles' introduction into the Ultimate U will be a great jumping-on point.
Sadly, some comic readers and news outlets have reacted negatively to the move, alleging that Marvel's reasoning behind the new character isn't one of promoting diversity, but a politically correct publicity stunt. For his part, creator Brian Michael Bendis stated he was inspired by Donald Glover's campaign to be cast in the title role of the upcoming Amazing Spider-Man movie (Andrew Garfield ended up getting the role).
As much buzz as this story is creating, I find it ironic that more outlets haven't mentioned one of my favorite characters of all time in the discussion--Miguel O'Hara. The Spider-Man of the 2099 universe was of Mexican and Irish descent, and he first came onto the scene in 1992.
In any case, kudos to Marvel, who, after their latest "Comics for Comics" makerting stunt, needed a little positive publicity. Now let's hope they do the character of Miles Morales justice.