Update: As has been pointed out in the comments, everything I've said about this DLC being free is not entirely true. I can only assume that the panelists at PAX were unclear about the issue. Some sources have since changed their articles dramatically without clarifying the edits. They also have freshly scanned copies of the concept art from the presentation, which appeared rather suddenly.
What's now being reported is that this DLC will be released 2-4 months after release, but it will be free for those that preoder. Those that did not pre-order will have to pay for this DLC. Yeah, kind of ruins the tone of my article, doesn't it? Sources are now reporting that Randy Pitchford is quoted from the panel as saying the DLC price will be, "comparable to most DLC."
I take full responsibility for the error. Sorry folks, dropped the ball on this one. Though there are some suspicious details about the whole scenario.
During a PAX East Gearbox panel, a question popped up that most Borderlands fans have thought about, "Will there be a fifth playable class in Borderlands 2?" And when Randy Pitchford replied in the affirmative, it's fair to say most gamers were surprised/worried/suspicious -- what was the catch? Pre-order DLC, day-1 DLC, something gamers will have to pay for? Not at all, apparently. Randy said the current plan was to introduce the Mechromancer post-launch as a free download for all players.
The Mechromancer will fill the Borderlands pet class void. Growing up as a poor, half-robot girl can be difficult, so why not build yourself a Deathtrap companion to ease your loneliness? Sporting red hair and goggles, with a mechanical arm, I almost thought she could be related to the original Borderlands' Siren, but the eyes definitely don't match.
She's still a long way off however, still in conceptual design actually. Gearbox loves to share its fun with fans though, and introducing a character at a PAX panel is quite awesome of them. Announcing they're planning to release her as free DLC is great marketing, to boot. Perhaps to mock Mass Effect 3's day one character DLC, or perhaps just to show they're paying attention to what consumers want, Gearbox took the time to show us something cool they're doing. Gamers remember that sort of thing.