I played the weekend thing in my free time. I'm still not too sure about this game.
For one thing, there's a lot of missions that really suck. The Prince Rurik missions, which all revolve around escorting an NPC moron around and making sure that he doesn't die. It's not so much an issue of him being moronic, but that is an issue, it's more a matter of wondering why you have to make sure he doesn't die. If a player dies, you can ressurrect them. If a henchman dies, you can ressurrect them. If Prince Rurik dies, the scripting kills all the players and the mission is a failure. Why is it like that?
Escort missions really aren't that cool in most games, and too many games have them. However, in a game like Guild Wars were ressurection is pretty easy and only takes some time, they make no sense. Keep someone alive or else everyone dies and you have to try, try again. Things like that pretty much suck.
In the open weekend, there was a mission that involved getting crystals to pedastals. If you got all the pedastals filled with crystals, your team wins. If the AI enemies do it, everyone dies and you're back to try, try again. While this might be a fun mini-game type thing, that sports arena style scenario takes place after a trudge through the jungle, killing lots of monsters, this and that, blah blah blah. To go through all that just to win something that seems more like a Tribes multiplayer game is fairly crappy.
That's one problem I see with this game. A lot of the missions are very long, and there are some questionable aspects to them. These are even more questionable when they occur near the end of the mission, which means you have to endure the whole thing over and over again. I can see a lot of people playing the game and getting feeling of Just get me through this one mission, maybe the next one is more fun. The problem will be that maybe, just maybe, somewhere down the road you'll want to try out a new character. That character will be inflicted with dealing with missions that may have given you a headache the first time around, but will be genuine torture the next time.