The new Xbox magazine I got today had a long article about RSV2, and it sounds great! Now the campaign will be exactly the same in single and co-op modes. Also friends can jump in and out at anytime, and you can continue playing the campaign w/o restarting.
They are also adding a similar scoring system like COD4 to unlock equipment. One neat feature with that is if you decide to complete the campaign (in single player or co-op) first and unlock all the equipment it will carry over into multi-player not forcing you to start from scratch, and visa versa….
This is a definite buy for me!!