I was the same way...stun grenades all the way because they threw faster than the flashbangs. Even though they took the speed that I liked away, I'm glad they did, because I feel that those two tactical grenades are now on par with each other. I guess they could've sped the flashbangs up and I would have been happy too. Lethal grenades haven't changed except for when you get Quickdraw Pro...with that they throw much faster.
Just glad they made both stuns (now concussion), and flashbangs equally viable for use.