Technically the Guardian was going to be my main, but after playing it in BWE1 and the playing the Mesmer, my second choice for a main, I dropped the Guardian and knew then I was going to main a mesmer. I LOVE it. Greatsword/staff is my current set-up and I think it works best for me so far. They both compliment each other very well, and both give me options every fight.
I have been doing a bit more WvW than PvE the past few hours and I have to say, WvW is extremely fun. If my server was not getting dominated by a PvP server, I might level up only that way. However, since it is, I am forced to do quests