I like a lot of the aspects of this game. The graphics are really nice, and it sounds good, and the basic tower defense systems seem like a lot of fun--building towers and then piling them up with cannons.
My primary gripe with the game is just that it's too hard. I haven't been able to beat level 2 even though I've tried a number of strategies. In fact, I haven't been able to get past the first wave of ships without losing at least one life, and I'm honestly not even sure what else I can try using the money at the very beginning of the round...
But if those gameplay problems are ironed out a little bit, I would say this game would be pretty darn good. I had quite a bit of fun playing it as it stands even though I don't really see how I can win, and I actually think that there are a fair number of good ideas in the strategy of the game right now--for example, how it is always better to buy 1 chain gun then 1 normal gun, then to buy 1 normal gun then 1 chain gun (i.e. that mechanic seems pretty fair and makes it so players need to pay attention to what they're doing).