OK. You have dragged me out of lurking for this. Any momentum in the bar is initiated by the muscle contraction and is hardly indicative of a useless rep. I don't necessarily recommend maximum speed but momentum is not magic, it had to be put there.Well, to me it isn't, if we talk about anything over a single rep the positive portion of the rep, you push as fast as you can, if you are doing 10 reps for example, you will have fresh strength you will be able to push real fast, maybe one second, most of which will create momentum, useless.
move at a controlled speed instead, and maintain that speed until the last rep will ensure safety, and an sure your being honest with your progress.
the argument, move fast to make you fast is bullshit.
Where I will agree with you is the stretch reflex. A muscle will store energy in the stretch for something like 4 seconds so a pause at full stretch may be beneficial.
Personally, I think the weight will dictate speed to a large degree but there is room for trying lighter weights and making cadence the main focus once in a while.