TL;DR: This game is absolutely fantastic with a friend and gives hours of fun content.
Overall Score: 9/10

Pros:

- Fun take on the tower defence genre with a mix between traps, defenders, weapons and trinkets.
- Meaningful and correctly paced progression that you're able to swap out for different upgrades at any time.
- Levels are designed with 2 people in mind meaning you don't just stomp with a partner.
- Both classes have some cool individual special weapons and stats so it's great mixing two player's abilities together.
- Easy to navigate interface.
- Combat is fun and engaging, you're always doing something.
- Different enemy types and maps force you to change up things each level/wave so you're not following the exact same strategy each time.
- If you own OMD1 then you gain access to some of the original maps edited for OMD2.
- Combos force you to use different traps and think outside the box to maximize the scores you get.
- Different difficulties and Endless mode leaves you plenty of opportunity to replay the game.

Cons:

- You may have to disable RazerInGameEngine to stop the camera spazzing out.
- No support if you have a game crashing bug.
- Highscores are plagued with cheaters which won't be removed as the developers went under.
- The sound for the intro and cut scenes cannot be lowered so prepare for earrape. Spam press spacebar and you won't have to worry about them after you've watched them once.
- The DLC's only offer 3 levels each which is a small let down, but they're very fun and unique.

Scoring:

Gameplay: 10/10
Sound: 6/10
Graphics: 9/10
Servers: 10/10
Enjoyment: 10/10
Replayability: 9/10
Overall: 9/10