Haven't tried online yet. Just finished the attitude era mode+the off-script challenges. Took me about 12 hours. Pretty cool stuff. Still there are some glitches that can be really annoying, like opponents getting stuck IN the mat, or the camera fukkin it up and keeps on zooming in. Furthermore, those title-belt entrances are as good/weak as last year. It's a pretty cool game, but not worth $60. Besides the DLC only consists of characters, titles and moves. Wish they would add some storylines (like the attitude era mode) too that as well.
Now on to the WWE Universe mode and unlock all those achievements.
Most difficult matches: NAO vs LOD and Jericho vs Road Dogg
Oh, and as far as I could see, no GM mode. You can create your own events and arenas, but there is no such thing as a smackdown vs raw mode.