I thought it was time to buy a new Mac, due to its sluggishness. Wrong!
Adding 4GB of RAM and replacing the 5400 rpm HD with an SSD has breathed new life into it. To quantify; opening Adobe Photoshop took 1:00, but now takes :05. InDesign? From 2:00+ to about :10. Illustrator? From 1:30 to about :07. Booting up went from 3:00+ to about :30.
This indicates that the main bottleneck for computers is mechanical HDs, which appears to be a little-known secret. Save your money and invest in these upgrades...you'll be thrilled with the results!