Been playing the BETA, and the game is everything you've heard it will be, creative, innovative and really fun.
Best thing about it is just coming up with an idea, then spending hours trying to get whats in your mind on the screen, and working the way you want it to. You can explore other peoples work in a really simple way which means endless hours of fun.
It sounds cheesy to say but the possibilities really are limitless, unmatched replay value and what looks to be a strong community, even for the BETA phase.
All in all, good times. Buy it, you won't regret it.