I LOVE the campaign of this game. I've played through it entirely twice and played many other random missions. I think it's the best game I've played in a long time.
That being said...
The multiplayer on this game is absolutely TERRIBLE. I want to jump into it so bad and I want to keep playing GRFS so bad... but I just can't. I have never played a MP that is this bad that I can remember. The lag makes it unplayable. I can't stand shooting at someone to get no hits or kills half the time I'm playing. The gameplay is awful and the maps (aside from a few) are just terrible as well.
Of course this is just my opinion but it really sucks that once I'm officially sick of the campaign I'll essentially have no use for this game. It's a shame.