In an extensive interview with the doctors at BioWare, Gamasutra covers Star Wars: The Old Republic and their view on why it stands apart from other MMORPGs. The interview with Ray Muzyka and Greg Zeschuk is four pages long and covers quite a few topics on The Old Republic as well as touches on Dragon Age 2 and Mass Effect 3. In a choice quote from the interview on feedback, Ray Muzyka mentions, "once you've tried it, you just can't go back."
The reaction that we've had, and a lot of people playing it have had -- we've done a lot of consumer testing and there's a lot more to go -- but the common reaction we get from our fans when we play it, or the testers, ourselves, and our teams, is that frankly once you've tried it, you just can't go back. You don't want to try other MMOs anymore. I think that's what imbuing the game with a sense of heroic purpose and identity achieves.
Be sure to check out the entire interview at Gamasutra.