A few improvements make it a great addition, however if you are not a die hard fan, stick with 06.
PROS: Mometum meter makes games more interesting. You will no longer win every game in your dynasty by 50 points. Passing game has been fixed for the most part, and updated rosters are fairly accurate. More playbooks, more plays, more defensive plays as well. Online play has been nice. AI supports more conservative play styles. Do you go for it on 4th and 1 a lot? It's much harder to convert those now when you shouldn't go for it.
CONS: Momentum meter works TOO well sometimes. Teams that have no business beating you (if you are a top 10 team) like Tulane or Fresno State will be impossible to stop if they get the momentum. Momentum can be very difficult to get back. Running game is practically useless unless you have a 90+ rated RB. Sometimes the CPU is impossible to stop, CPU overuses play action and can be pretty cheap sometimes.
If you are a die hard college football fan and you need the updated rosters and playbooks, then by all means the $50 is worth it. However, if you don't need updated rosters and playbooks, then skip this edition and stay with 06.