Not sure if you're still reading these, but here's my take.
Graphics are virtually the same, as are most gameplay mechanics. The passing game is much more interesting and the defense "read and react" works really well for the most part. Recruiting is much better this year, and the game itself is very solid.
But, if you bought NCAA 12 (even 11 to some extent), this is hardly an upgrade. The reason I bought this game is because the ratings for each team in recruiting (Conference Prestige, etc.) is all dynamic now instead of being name-affiliated. If your conference wins a majority of its' bowl games, it will improve its grade. In my Offline Dynasty with WFU, I won the Orange Bowl, and several other ACC schools won their bowls and we went from a B+ conference to an A conference. (Tied with the SEC, which went down.) The Big 10 went to an A+.
Its all about what you want. The gameplay is slightly more realistic, the presentation is more detailed, and the commentating still sucks... about what you'd expect. Its the best one yet, but its not the best improvement they've made in their history.