Pretty good... But I had afew minor issues with both gameplay and style used.
The final boss has an obscene jump in difficulty, and it took me a couple tries to get it.
As well, the sheer number of skills and range of keys used to activate them made activating a skill when it was needed fairly cumbersome and difficult. On the final boss I ended up removing all of the abilities except for 3 simply to improve the ease of use, something I shouldn't have had to do.
As well, the skill trees could be completed before the final boss was reached, and most of the final skills for each didn't really feel like "Ultimate abilities".
The story was non-existant, and seemed more like an excuse to have a game than an actual story. When in battle, the background didn't really do anything for you, and while it was good it didn't detract from some of the busier moments in battle, it didn't create any flavor or add anything to the game.
Overall: Bland and clunky. Not terrible, but really not anything special either. Just another ship-based shmup, and not even memorable at that.
Next time: Make skill usage smoother and more rewarding, improve the scaling of the difficulty to be more reasonable toward the end, and try to give something more than just "ships shooting at each other."