This has been covered to a great degree, I know, however I shall add my own two cents for what little they are worth. Do I hate DLC? No, quite the contrary. Often, we are blessed with a creative work so complex and invigorating (be it a book, novel, or film) that we are moved wish it not to end. Dragon Age, to many, accomplished this. Other BioWare experiences have done much the same for me; titles like KotOR, Jade Empire (where is the sequel Mike Laidlaw?!) and Mass Effect to name a few. DLC permits this desire to be fulfilled, often to great satisfaction. Though, in truth, not always.
With BioWare I have not found myself unimpressed. Even Mass Effect's simple clothing DLC was enjoyable to a degree, but did not require you to purchase it to enjoy the core game. And really, this is where, for me, DLC forms a line between enjoyable and distateful. Any DLC that permits one to continue the Adventure after the core game is always welcome; however, DLC that is designed to be used in the *middle* of the story or provides a character which should have been included in the core experience is, frankly, disgusting. BioWare, against better judgement, has two such examples of the latter; though in the case of DA:O some steps were taken to rectify it.
Shale, obviously intended to be in the core game, was added for free to anyone who purchased the game new. Sadly, with Mass Effect 2, the final member of Shepard's "Dirty Dozen" was kept as DLC, and this frankly was a slap in the face to all of those who have remained loyal fans to all of BioWare's creative endevours. It was a blatant attempt to garner further profit for the game, not by it's creative merits, but by reminding the player that thier team was not trully "Complete" until Kasumi was downloaded. And no, the "well, it wasn't finished yet," does not a good excuse make. For shame, BioWare.
With that said, I remain of fan of DLC, BioWare's and other licenses, however DLC needs to remain an add on, a "post" adventure, not content that leaves one feeling as if the core book is missing chapters. DLCs either need to serve a "Prologues," i.e. Leliana's Song, or Epilogues, i.e. Witch Hunt. If you are an author, giving a loyal fan your newest book, but ripping out a few chapters before-hand and telling them later that they can have those missing chapters for a few dollars more is a deplorable course of action, and speaks poorly on the character of those who utilize it. Buisness is difficult in this day and age, I can understand this. However, profits can still be gained without cheating players out of content that, in many cases, obviously should have been included with the core game.
Keep DLC a "pre" or "post" experience and it remains a wonderful idea both creatively and monetarily. Remove chapters or characters from the middle, and it shows you no longer care for the fans, or your company is no longer your company, but simply a Figure Head in some-else's grand design for profit.