Okay, but too many flaws to be better than that.
The game isn't terrible by any means, but it sadly can be summerized into 2 words...
Easy and Repetitive.
The game was alright, but the moment you picked up a weapon that shot any type of rocket, you basically told the game that you are going to walk all over it, and there isn't anything it can do to stop you. Combine that with a shield that had more armor than your tank itself, allowing you to throw it up when your health started getting a little low and collecting the hundreds of repair and full(?) repair power-ups and still being invincible for the next 5~7 levels, and you have a game that can be beaten with little to no skill form the player.
I personally only made it to level 200, but I am assuming that the next 50 levels(Assuming what GuidoDeniz said is correct about 250 levels) would have been the same as the rest of them, seven or eight horribly easy waves of enemies, followed by maybe one or two moderate waves where things actually shot you.
What you could have done better...
With a game like this, the only thing I could see that you could improve on, without changing the entire game itself would have been to stop having enemies with the crappy machine guns, or no weapons, along with enemies that died in one shot at the latter half of the game.
Removing said enemies wouldn't solve the games repetition issues, but would possibly alleviate the difficulty issues.
Also, and this is probably because I was an idiot, but I didn't like having the space-bar being the upgrade button, mainly cause after I was done changing parts, adding points, etc. I seemed to find myself pushing the "Return to menu" button a lot, ending my game sooner than I would have liked.
All in all, it's an okay game, using a proven formula that seems to work for most, but with a few major flaws that cut it short of being better.
417709 before quitting.