Of course this isn't going to end terrorism. Some young fanatics are going to consider him a martyr and make more mahem accordingly. But he deserved a reckoning and a trial would have invited more danger. Those who lost loved ones on 9/11 have a bit of closure here. You take out one bad guy at a time, and face the next challenge. That's the real world, not a video game or Rambo-esque fairy tale.
If the 77 virgins await him, I hope they've all been very lonely and are named Horst, Rocco, Nasty Ned, etc.