New weapons and abilities are always going to be a nice addition but the improvement over C2 that I'm really hoping for is for them to tackle the MP lag. The amount of matches in C2 (on small maps with only 16 players) that were crippled with lag was morbid.
So far most of the iinfo I've read from the Dev team is focusing on the SP. While I think the console heads here (myself included) are more interested in the MP issues, the PC crowd were fairly pissed with the direction the SP took after C1. They weren't happy being transported from a nice, expansive, play-your-own-way jungle to a narrow city-scape played out through corridor like level design and staged set-pieces.
Crytek are really pushing the point that this game will be a lot more free roaming and even though it's still set in a city, it won't play like C2.