Efficiency Committee saw popularity when fast-advance was the bread and butter of every single Corp deck. The plan was : drop 3x Shipment from SanSan in your HB deck, find a window to score your first Committee and then wait for having a Shipment and an agenda in your HQ and score it from hand. Rince and repeat.
(Rule note : as Shipment From SanSan effect is to place advancement tokens and not advancing cards, this combo is possible).
It has gone out of fashion, apparently. People are nowadays more confident in glaciers and NAPD Contract became the 4/2 agenda of choice (two things that may be tied, if you think about it). Yet, the effect of EC is nice : gaining 3 to get whenever you want, isn’t it great ? But Corps don’t mind to gain if it doesn’t allow to score from hand, and the 3 influence points of Shipment from SanSan are better spent elsewhere.
On a side note, I used to use this rockabilly guy as an avatar on the french forum Run4Games and I’m waiting for a dedicated card. J’adore ce mec, il a trop la banane.