I have made a demo so you can try out the game for free.
Here's what you get:
- The first couple of campaign levels and songs
- All the tutorials
- Full two-player co-op support
- Save files carry over to full game
- Restricted to three custom songs
- No leaderboards
- No achievements (any progress-based achievements will be unlocked when you upgrade to the full game)
- Semi-annoying nag screens asking you to buy the full game
If you like the demo and want to move to the full game, I'd say around the end of June or beginning of July would be an excellent time to do it...