I just happened to notice this had been updated in Steam earlier today. The link below shows the full patch notes but here are the major changes:
- Added 5 boss remixes to the game.
- Added 1 new class.
- Added 4 new traits.
- Added 28 new rooms.
- Added ability to reduce shader effect quality for people playing on slower machines.
- Added 6 new Steam achievements (Steam only).
Good on Cellar Door Games for not only continuing to support their game but add free content. This pretty much solidifies my personal Game of the Year choice. I don't have time right now to check it out, but I know what I'm playing tonight.