Wingball (freeware) is available now for Windows as a playable technical demo with an online leaderboard. This project was placed on hold for the last year and has only recently been revived. I expect to release the next update in late January, 2012. At the moment, it's essentially a checkpoint racer with coin collection for high scores on a leaderboard, some weather effects and on-demand "bullet time". Other gameplay modes and levels are planned, as well as full support for Mac (and possibly other platforms). See the official Wingball site for leaderboards, project history and more.
Screenshot from Crystal Sands - Act 1, with "overgrowth" mode enabled.