This game is rad! It's visually appealing and the combination of a typing-rhythm game is novel. I can see it being a fun way to learn how to type faster. There's a few things that I though about while playing that could be cool additions.
The full words mode was my favorite, and is an opportunity to put some humor into the game with funny words or sayings. A similar game where you needed to type the lyrics of a song at the right time would be fun too...
With the words scrolling across the bottom of the screen, it means that visually the player is always focused in the same spot (generally the lower left, with occasional glances to the right to check for new letters). It might be nice if the letters flew in from all different angles to add more challenge, and to focus the player's attention on different areas of the screen.
Finally, the blue wavy line graphics sometimes obscure the letters as they scroll, but this is a minor issue.
Cheers, and nicely done!