Capcom has announced that the first wave of downloadable content for Mega Man 9 will land on XBLA this Tuesday, not even a week since the game debuted on the service. The content available will include a playable Proto Man and a new gameplay mode called Endless Attack (you can probably guess how that one works). Official prices haven't been announced, though Proto Man and Endless Attack cost $2.00 and $3.00, respectively, on Nintendo's WiiWare service. Of course, we can't properly gauge what it costs to convince yourself that Capcom isn't screwing you by charging for modes that should have been included with the game in the first place.
The remaining bits of DLC are expected to arrive the week of October 20.