I've been playing this series since the first one, and from the transition from AWDS to DoR is very big.
All the old CO's that I've come to know and love are gone and powers have been toned down. (No more Super CO Powers and Dual Strikes)
You can get a CO Zone, which allows you to put your CO in a unit and give a bonus to units arround you, this adds far more strategy than instant game breaking powers IMO.
But, I highly suggest this still, the learning curve takes all but the first few missions (where they teach you little tidbits anyway) and Wifi battles will always be a fun edition. Though I do warn you...multiplayer games with humans can take ages.