That's true. I played for 3 hours without realising but the repeating of battles does take its toll on the boredom side. Other than that I enjoyed it.
Fun is too keep changing the robot parts until you find one that completely fill you playstile. Except that when you reach half game and you get the flying model. After that the every battle of the game is deceided by Jump, hover to the oposite side of the screen, shoot main weapon and missles, drop, release mines, jump, hover..... You can beat EVERY boss in the game with that strategy without getting hit. Besides, if you follow the game without that, you can expect a awesome challange in the last battles! (still its a wise Idea to keep the parts in a emergency lol)
I agree with TOD, it just gets repetitive, even though there are tons of parts for your robot, you're just doing the same thing over and over again...