Upon receipt of NHL13 you will need to pull down the 37MB patch (1.01) for your brand-new game. You'll also want to download updates for a few tuner/roster settings. Having played 4 games online thus far, I'd say it's pretty consistent with what you'll experience if you've played the demo. Player speeds seem to be a little more noticeable between characters (in otherwords, if you've set your accel/speed higher, it should pay dividends compared to last year). I haven't received the boost pack code from amazon yet, but I think the terms/conditions say they've got ~2 days to e-mail that.
Graphics: A lot more polished compared to last year. The character renders are really solid and the overall presentation has fewer delays. Otherwise, a lot of the animations seem similar to previous years, though some physics tweaks have already brought about a few comical collisions.
Audio: The commentary has been updated, as has the audio track. It's nice to get new music, but note that you can pull your own tunes off your PS3 using the "EA Sports Media Hub", going into "Custom Music" and then pulling in your own songs (you've put music on your ps3.... right?). After a few days, I typically turn down the in-game commentary. I got really tired of hearing "a soft dump into the corner" during NHL12 every 10 minutes -- this is in reference to a play where forwards send the puck ahead into the offensive zone aka "dumping the puck."
Gameplay: It feels pretty different with the addition of more flexible backwards skating, new physics on your skating mechanics and more "bumping" other characters. Already, I've heard people in-game complaining about "interference" from other players who skate into them without attempting a check -- this will not result in a penalty but might be just enough to take you out of a critical play. Pokecheck is really powerful now; as a defenseman, this was something I really missed last year. I have a feeling the developers will release a patch that tunes down the pokecheck in the near future. At least it's not as bad as the hipcheck-gate issue at the beginning of NHL12.
Sony/EA need to stay on top of game releases. You can't buy any boosts or slots as of the time of this writing (I was trying to get another slot). You'd think Sony could go ahead and make that available the day before the game is released. A friend who is playing 13 says he'd give the game 3 stars, as it feels like the same old grind, year after year. There's some truth to this, but I really enjoy getting online to play with friends. You see something new every time. In that way, it's like real hockey, you never know if someone is going to go flying into the bench (probably not) but who knows? Maybe next time I play the goalies will get into a fight... that'd be great. If you liked NHL12, go ahead and get '13.