A few things. First of all, I love that you've got all sorts of words in here. The other reviewer says that many of these words are beyond the reading level of a lot of people today, and I fear he's correct. This is not a good thing. I suspect most of the low ratings on this game came from people who are frustrated by the big words and are more content to be ignorant than to expand their vocabulary. That, or they just have no interest in spelling and vocab. Of course, maybe I'm just a prude, because I know most of the words on here. But God forbid a game is educational, right?
I have a few problems with the gameplay, but they be more my problems than yours. First of all, I when rushing for time, I have this tendency to hit the space bar too fast or an extra time, causing the next word to vanish before I even see it. My fault, but a dumb way to lose.
I'm also not sure I like the idea "5 mistakes and you lose," because when typing fast, one little mistake generally results in a whole string of mistakes at once. I accidentally hit the wrong key, miss a letter, or hit two at once, I generally lose a bunch of tries because I typed the letters that came after the mistake and the game considers those to be further errors. On the other hand, you do haev a buzzer that goes off to warn the player of a mistake, so it's really just a matter of the player being a clumsy typist. So, an expert touch-typer might have no problem at all. Therefore, it's more my mistake than your programming. But that mechanic still frustrated me.
I loved seeing a so many of those cool SAT words, though. Since I do use a lot of them, and many aren't spelled as they sound, it's good practice for a writer like me.