I played him at Pax East last weekend. This is the first time I played Overwatch ever! I fell in love with the Reaper once I tried him out. I also made lots of work.

I believe his strengths are flanking and eliminating people from behind. He finds cracks and openings in the enemy team. In corridors he is dominant unless if there is a shield on front of him. He does die quickly but his high DPS is what makes up for it. If the enemy team is going to stick together, they need to watch their 6 or they will eat a Death Blossom or worse. Shadow step is really good but if used incorrectly it can just waste your time and get you killed (given its long start up and recovery). Wraith form is amazing for retreat until you got someone really determined to hunt you down.

I found his weaknesses to be the long range game. Any character that out zones Reaper or can retreat and shoot the same time can screw him over. I don't believe he should ever be in the middle of a giant shootout. Maybe he can hang there just to teleport but he shouldn't be there just for more fire power. Wraith Form should be used wisely or he won't retreat when he needs to. If someone hunts him down after his wraith form... tough luck

Overall, he is a really good assassin. If the enemy team does not prepare for a Reaper, they will get destroyed.