While not nearly as much money as successful triple-A commercial game titles, this is a huge success for indie game developers. The $1.8M came in from 232,845 sales. The average Linux user was paying $13.76 USD per game bundle while Windows users came in at just $6.67.
More details can be found at HumbleBundle.com. Based upon the email sign-up to be notified when their next project launches, it looks like there will eventually be a Humble Indie Bundle #3.