IGN just posted a write-up on some of the changes and improvements for "Superstar" mode in Madden NFL 12: http://go.ign.com/mU8niW

They say football is all about "team," but who doesn't come into the NFL dreaming of being a superstar? Developer Tiburon is hoping to make gamers feel like gridiron studs with some long-overdue improvements to Madden's Superstar mode.

Superstar puts you in the cleats of your own created character, just as it has the past few years, but now you have real control over your player's destiny. Gone are the arbitrary attribute bumps, the pointless practices, and the feeling that you're working towards nothing more than the next game.

The whole point of taking over the career of a single player is that you're going to raise that player from practice squad walk-on to Hall of Famer. And a big part of that experience is being able to choose how your player improves and the type of player you become.

Superstar mode is now built off skill points, which you can spend however you like -- focus on speed and spectacular catch ability for your player or dedicate yourself to becoming a powerful possession receiver. Points are earned for your performance on the field and for completing practices, but those points are never tied to any specific stats.
Hit the link to read the rest of the write-up and visit the image gallery for new screenshots from "Superstar" mode. Apparently IGN will also be posting a write-up talking about some of the "Franchise" mode improvements for Madden NFL 12 tomorrow as well.