I like the classy look they give to my guitars, besides protecting the paint job I think it dresses them up nicely . Obviously I like my guitars to look as minty as possible...no road worn, relic, etc. for me!!!
usually if the pickguard comes with the guitar I will leave it on, my larrivee has a clear pickguard which totally rocks, my current LP special did not come with one my previous one has a pickguard attached to the body, so was not a choice there, my epi has a very cool looking pickguard so really would not take it off unless it was broken.
For Les Pauls, off it goes for me. I took it off mine and have never considered putting it back on. They feel like thier in the way to me and there's only a couple finishes that I like the looks of them on.
The entire idea of having a beautiful <insert price here> guitar then covering it up with a piece of PLASTIC just makes no sense to me. Furthermore, any ideas concerning attaching pickups to said piece of plastic can also be dismissed.
Skip the pickguard.
I'm a little fanatical about keeping my stuff in good condition so I never remove pick guards. I just picked up this guitar which has no guard and I tried using a couple of sheets of that clear plastic they sell to protect the screens on PDA devices. The are suppose to be removable... held on by static I believe. I did a pretty messy job of applying them but they are invisible at more than a couple of feet away.