The GvE edition gets you new costume pieces including a couple of new permanent powers including jump jet pack and a Pocket D teleport power. New veteran awards gets you all sorts of new costume pieces as well as permanent new powers, Sands of Mu or the Undead Slaying Axe.
http://www.cityofheroes.com/store/go...gve_items.html
http://www.cityofheroes.com/communit...anrewards.html
If you already have COH and COV, you can get the pack for the extra in game parts. $10.00 bucks gets you all that fun stuff above.
As for AI on the enemies, I do notice a big difference as they are scaling towards the team that you are on. And once you do hit the mid 30's and higher, the enemies tend to do a lot different things.
And hey, when you are with Roleplayers, the story behind the missions never is the same.
