As others have stated, "It depends".
If there's a red light a block ahead, I accelerate rather gently. I don't see any point in racing to a red light. If I'm on a freeway on-ramp, I accelerate to the speed limit BEFORE I have to merge.
In my experience, unnecessary braking is more detrimental to fuel economy than (reasonably) enthusiastic acceleration.
As long as your acceleration doesn't cause an unreasonable need to brake, have some fun.
