If you get it for PS3, make sure you patch it (most people do, but I know a few people who usually don't). There are some issues with the game out-of-the-box, but patches fix em. But yeah, fantastic game, and it still plays great on the PS3. DLC wise, make sure you get Stone Prisoner (it comes free with new copies), because it adds Shale, maybe the best character in the game... well, ONE of the best, Alistair is pretty amazing. I would also get Leliana's Song and the Darkspawn Chronicles, which are separate campaigns, but very interesting. Witch Hunt, Warden's Keep, and Return to Ostagar you should only get if you're really in love with the game, because they're not great DLC, honestly- not terrible, but too short and disappointing. Haven't played the Golems of Amgarrak.
Great, great game. Liked it better than ME1, but not ME2, methinks. Got Dragon Age 2 preordered, though- can't wait to play as Hawke!