Since no conclusive details have been posted on the wiki and I finally got the bloody thing myself a few days ago, I thought I'd share with you all exactly how it works.
It does not grant bonus EXP - I can confirm this from landing several killshots with capped Gold & Ebon lights after hitting 610/kill in a worms party the other night. That party had also been slow to start up and I was there from the beginning so I couldn't really tell how exactly it worked until earlier tonight.
I was in another Worms party, but this one had been going for a while unlike the previous one, so they were already capped on EXP & Lights. Normally in this scenario I'll be stuck in the low 20's and gradually move up but instead I got about 46 EXP right off the bat and within 30 minutes was netting over 400/kill. I've never seen my EXP per kill climb so fast before, which leads me to conclude that the perspicacity abyssites affect the rate at which you cap EXP/kill.
This makes meriting much, much less painful since now you don't have to wait as long after dumping them to climb back up to optimal EXP. I'm attempting to beat 3 more Abyssea bosses so I can acquire the Ivory abyssite and see how much of a difference having 2 makes.