After my wife's repeated complaints on the performance of our family iMac, I have had to do some housecleaning on it and found out that it was spending an inordinate amount of time swapping. And having looked into that in more detail, I also realized you couldn't control OSX swapping policies the way you can on Linux so I did a number of mundane cleaning operations but the most effective seem to have been the following: forcing OSX to purge at regular intervals. It seems like the operating system ought to do a better job of it but this simple step has helped limit the amount of swap consumed. I ended up implementing this on all our macs, irrespective of whether they showed signs of swap strain or not.
featherweight:~ arno$ sudo crontab -l
*/15 * * * * purge