Excellent. Challenging and addictive. I see only one little problem : upgrading the medic is way less effective than the others - I tried various combos among my games and the one I invested in the medic was the more difficult to win. Fortunately, you can take back your choice, so this little imbalance is of no consequences.
On a technical note, the last trophy, "100% campaign completion", doesn't register on my account - although I beated the game three times in three different days... Does anyone have the same problem ?