Actually pretty good.
This is an interesting concept. You seem to know the proper timing of when to end the game in a satisfying manner too-I finished without feeling that it was either too short or too long.
It boils down to trial and error-and then memorizing the words before the added P, though-especially with the special words. The special words in particular seemed to be like an added gimmick just placed for the fun of it, as they don't appear often enough. And then, the boss fights all boil down to slipping between columns of bullets. Nothing too fancy, except on the last one, where you're forced to dodge right.
The ship is wide and the player is constrained to moving only in the x axis, thus it's rather hard to easily weave around obstacles. However, after playing through the game, this turns out to be the right decision; making the ship smaller or allowing vertical movement would make the game way too easy, especially during the boss fights.
The music is a little dull, though, (maybe you should change the instruments to make it bright and thus convey a sense of intensity like the majority of SHMUP games) although the explosion from the missile made me think back to sounds from Gradius III for the SNES. Even the Split Meteors remind me of Gradius III.
Graphics seem fine, although the particles that the mothership shoots and the lasers you fire look too rough and simple. To me, those two things were the major detractors in the graphics for the most part, and in fact made the game seem more primitive than the rest of the graphics show.
Unfortunately, there were also only two forms of minor enemies--thus two patterns to look out for during the main part. The meteors were okay, but the word pirates in particular could have employed other patterns than charge straight down. That also detracted from the feel of what I'd usually call a good SHMUP game.
The ID armor system for the enemy ships works well for the most part. I believe there is at least one glitch. I've seen the word sell. By shooting it, it creates the word Spell. However, the game didn't accept the word, and counted it as a 0.