Multiplayer's fun, as long as it's a private session with friends only. Playing it with randoms is just irritating and frustrating especially since most people I've run in with would prefer to just kill you, wait for you to respawn then kill you again.
And if you run, they'll continuiously chase you down, kill you and etc etc etc.
So, no, not enjoyable whatsoever when people care more about killing everyone else than doing the multiplayer challenges and other features. e_e;
However, I quite enjoyed myself when playing with a friend of mine in a private session. Now THAT was fun.