Proceed with caution if you're on your own, though.
I say this because I ran into it A LOT over the course of the single player campaign. That's because a. the AI is a bit unbalanced, with folks either moving about rapidly or needing to be healed themselves, and b. enemies that are so dead-on in finishing you off, you barely have time to save their skin when you're maintaining your own. (And that's not even including the armored guys.) You can jump in-between players, but that requires taking a break from the action (hard to do when you're under fire) and then warping into someone who could be in even more peril. The AI behavior isn't completely ludicrous, but you can just tell that the game wasn't built for grinding on your own, like Insomniac's previous Resistance trilogy.
Where Fuse fares best is in its co-op wares. Up to four people can join in as each individual soldier and do some MAJOR damage. Seriously, when you combine all the Fuse effects in each weapon together, it's something of pure genius, as you build up a high score and watch enemies evaporate in a number of ways, from melting away into hot butter to creating a chain reaction of planet-like explosions. It's really something to experience – and probably what Insomniac had in mind all along when it started the project.
In addition to the seven hour-ish single player story mode (which is acceptable, though Insomniac told better stories through Ratchet and Clank), you can move on to Echelon Mode, where you face waves of enemies either on your own, or together as a group. Obviously, group is better, though you need to make sure you're on the same page and prepared for a challenge. Otherwise, you won't be grinding levels much.
