A quick poll if you please.

TheBigDipper

On. 

TonyR

On, on and thrice on.

proggy

Either on or better still fit soapbars (cream ones)

Winny_Pooh

Pickguard on? Covers on
Pickguard off? Covers off

axisus

On for me.

Voxman

For a LP I'm  traditionalist - pickup covers on always, and pickguard on too.  In fact I dislike open h/b pups generally  and never understood why PRS Cu22s had pup covers but Cu24s didnt...but at least the Zebras on my Cu24 make it look a bit nicer. 

UnclePsychosis

On. They look awful off. 

Philly_Q

ICBM said:

On. Cream bobbins in a sunburst Standard looks terrible, like 70s DiMarzios. (Which are good-sounding pickups, but look awful.)

I tend to the opposite view, I love that double-cream DiMarzio look.

On the original question, I'm going to hedge my bets... if the guitar is vintage-style, a bit mellowed-looking, nickel hardware etc I'd keep the covers on.  If it's new and shiny with chrome hardware I'd take the covers off.

thomasross20

Off sounds better (I can honestly tell the difference)

LordOxygen

eSully said:

LordOxygen said:

On, cream and zebra ones look gash imo, black aren't great either. 

On a honey burst I'd agree but on a black LP zebras look awesome 

We'll have to agree to disagree. 

Bucket

On.

Rocker

On.

crunchman

For looks on.

Sound is far more important though.  They will sound slightly different with or without the covers.  Generally slightly less high end with the covers.

RandallFlagg

Covers on on Standards, off on Customs

nick_s

On for sure.

frictionfraction

None so black....Black les Paul, black everything else, uncovered black pickups.  Just placing my order with oil city for a pair of uncovered nightfighers and then I'll post a pic... together with my black tee shirt, black jeans, black socks and pants. Apparently black is slimming ... I need all the help I can get 

Alterlifeson

Depends!
Black LP custom - either
LP Standard - on
SG - deffo on
Superstrat - deffo off
PRS - off on 24 fret models on on 22

olafgarten

I think the only time an uncovered humbucker is acceptable is on a Strat. 

zepp76

That's that confirmed then, I had a funny five minutes where I thought off might work but I've come to my senses! Thanks all.

DannyP

On for me.