Absolutely love it.

This game is amazing.
At 1$ Id recommend it to anyone.
It looks like a lot of work went into the making of this game, its original and its fun.
If you like musical tap games such as tap tap revenge, dance dance revolution or bit trip beat, get this game.
I have a few minor problems:
The scratch and flick notes dont work very well for me =
The in-app purchases are expensive (1$ for one song? 1$ for an avatar?)
Considering they dont really do anything...
Butterfly, stage is flipped... So?
Bird, points torwards your level are tripled... Im at max level anyway.
Human, reduce the groove requirement at the end of the level by 30%...
I havent had any trouble finishing any level (except the space invaders on hard) which took me 2 tries.
All the avatars for purchase are fairly useless...
And Id like to see a few more songs included in the original price...
Another aspect I dislike is how ranks are determined. It seems that the rank you get is decided by how many great regular notes you hit and not at all related to the total points. This makes it pointless to aim for ad-libs as they dont seem to count for s-rank for me.
Id make the ranks based on the amount of points accumulated in the song, making the chain multiplier and ad-lib notes more sought after.

After update:
Price rise to 3$. I still think its worth it to buy the game...
Couple of free songs added, though 2 of the 4 new songs cost money >,<
still the same problems as I stated above.

GL1TCH3D about Groove Coaster, v1.1