Up until the end of the beta it did work and it's increase would be noticeable in the ship's power management screen. What Geary says is correct though, so you may not see the effect if you are in sector space.
I'm not sure about the numbers, but yes, basically it boosts your power levels resulting in heightened efficiency. The effect is bigger on the lower power settings though.
The biggest bonus you will get out of it will be when you have your engines set to 25%. It will probably give you a 6, or so pointish increase to your engine power level at 25% up to like 31ish, but at 100% you would probably get like 1 point.
i have my power settings at 70/55/25/50 with warp core theorist and 9 skill in warp core training, my power levels are 70/57/32/53 so yes it does work iirc the bonus goes up slightly as you go up in tiers of ship, but i could be wrong