Eye of the North is great fun, though it makes more sense if you've played through the Prophecies campaign from the start. Unfortunately, that's a lot slower going than Nightfall or Factions, as the quests give measly 500 xp rewards and the storyline progresses at a snail's pace. It's something you should probably try anyway, but I don't think I could ever go back again. :S
But you can still come play in Eye of the North with me!