First off, congratulations on the 1 year anniversary and getting us our long awaited Mac version!

I just have a few problems to report.

When I launch the game, it goes into windowed 800x600 mode with letterboxing. But trying to change to Fullscreen or change the resolution won't work. The buttons don't seem to want to activate. Pressing Space or Enter doesn't do anything.
Next, the Quit command doesn't work either. Press Space on the "Sure you want to quit?" screen won't do anything. I just use the X to close the window.
I had the game crash as soon as I entered the WARP ZOOOONE!

in level 5. I relaunched and none of my progress was lost and the warp zone was unlocked so kudos on a smart saving system. Still, it was odd because it did it right after the voice said the words but the animation didn't get to complete. Edit: Yeah. It's definitely the "animation" before the level starts. As soon as the animation ends the game crashes. So I can't actually play the Warp Zones yet.
And lastly I did have it crash once when I went to quit with the X button before actually going to the "Sure you want to quit?" screen first.
I was hoping other Mac users might have the same problems and they can get a fix out. So far no game breakers. But I'll keep playing. Until then, is there a way to set the game to fullscreen and 1280x800 through the command line or something from the Mac version on Steam?
Edit: Oh, in case you need it, my specs:
2010 MacBook Pro
2.4GHz Core2Duo
8GB RAM
128GB SSD