I tried it myself, and I sorta don't understand why it carries a level-system? So far, it only unlocks cosmetic stuff, and the unlockables are a point-buy system with 1 point per level earned, and I would suppose the heavy and light frames, but that's just about it. You'd expect it to play more like Borderlands's model, but not really. It's also not as easy to tell whose on what team as easily (color coding seems to be lacking a tad, unless you recognize outfits in a nano-second up close (too much friendly fire on my part if the glow doesn't appear in time, and my only other hint is if the health bar is of an opposing color).
Weapon-wise, I've optimized my weapons to their most effective/efficient models (beat all challenges up to at minimum 2-stars, that's all that's needed, the tutorial, and a slightly more difficult one of the same thing), end result, the weapons seem a tad unbalanced, even when all of them are fully optimized. SMGs just mop up the field more effectively than pistols, and machine guns. Sniper rifles seem to be low in ammo, and the grenade launcher gives you only 4 shots.
This would be a fun game with a good few people once in awhile, but nothing worth a long-term investment in. Haven't tried campaign mode, but I think it'll play much like Unreal Tournament III, and just use deathmatching as it's grounds for story, and explain why nobody is dead forever.