Very fun, with extremely solid and responsive shooting mechanics and very fun and fluid gameplay, all presented with a crisp and futuristic art-style and filled with well-designed simple-yet-elegant enemies.
Its only drawbacks, I feel, have to do with the upgrade system. For one, the upgrades are too simple and unimaginative, and two they're limited entirely to stats. If there were more imaginative and unique upgrades, and more importantly if they were reflected in some way in the models themselves, it would lend a lot more weight to the system as a whole. As it stands, the upgrade system just isn't very good, which is odd considering the nice selection of guns. Secondly, and this is a very simple thing, I think the scrap fades far too quickly, and that you should just tack on a few seconds to its timer.
Other than those two complaints, the game is as I said fun, fluid, fast-paced, and exceptionally pretty. Very good job.