I have been playing around with Aceton Field II on my T5 Fed character, but queues are so long that I've only done a few games, and the maneuverability of the T5 Cruiser is not really conducive to getting a lot of use from a 90 degree arc ability.
I did notice that while the tooltip indicates it does damage to the target every time they attempt to fire energy weapons, the actual effect seems to be just a straight (very minor) DoT. Apparently my dream of watching a Bird-of-Prey melt itself with Cannon: Rapid Fire will not be coming true.
That being said, still, cutting the target's damage output by 50% for 25 seconds seems like it could be pretty useful. Although I have no idea where that -50% gets applied; it could be reducing just base damage, it could be factored in at the very end of damage calculations, or anywhere in between.