Yesterday I was working on a document from another office so the server wasn't in the building. I was working on graphics that required hi-res display so I could use them as a guide, but because they were all on the server the performance was abysmal. I realised after a while what the problem was, copied them to my local hard drive and re-linked so everything was much faster.

InDesign should be able to do this automatically: when a large image is not on the local drive, a copy of it could live in a cache somewhere to be used to generate the hi-res previews. If the server image changes, the local copy can simply be refreshed. It would greatly speed things up and avoid having to maintain and link to different sets of images.