Short but fast-paced, fun, and exciting!
First off, I'd like to talk about the single player. I have not yet completed the entire campaign, but so far all of the action is very fast-paced, and exciting. Some levels are very short, and others are almost impossibly so. However, some levels can be more difficult, but nothing has been too hard. The combination of relatively easy levels and incredibly fast paced gameplay make this a very fun single player campaign.
The other big portion of this game is the complex and intense customization. Everything from paint to the immense amounts of weapons. The weapons can be equipped and unequipped for a price, and they can be set up to your preference of close quarters, high impact laser blade combat, or long-range, high-powered sniper cannons. There are easily a hundred weapons, and probably dozens of base AC's. Together with the intensely customizable paint options, this results in millions, if not billions, of possible combinations for you to custom build and custom tune your AC to your personal preference.
Sometimes the game will through you a curveball or a map will be so bright you cannot clearly read the radar. This, however, does not affect the gameplay too much. occasional visual glitches make the game great, but not quite awesome.