I just played the game for the first time and Mercy is the most fun I have ever had playing a "healbot" class. Blizzard fucking nailed it. The split second, CONSTANT decision making between heal beam and damage beam, who to use it on, and how to best fly around using her Shift is so friggin enjoyable. Wow. I usually hate this type of character but I'm absolutely blown away by how much fun I had even when my team was losing.