However, I am running a little low on drive space. What difference would that make?

Fragmentation. As you run out of drive space HFS+ will get more and more fragmented and you run out of spaces on the drive where you can write a big hunk of data consecutively. Swapping to a file on a fragmented drive can be particularly nasty because the system ends up allocating a swapfile that is all over the drive so it has to seek like crazy which slows down swapping considerably. Norton Speed Disk and Techtool Pro are two utilities that will attempt to minimize fragmentation, but if this is what is causing you problems it will happen again sooner or later if you don't free up some space. I try to keep at least a gig free on all my machines or use a dedicated partition for the swapfiles.

-Mike