Upgrading the RAM of your Mac is often the cheapest way to make programs run smoother. When you are running multiple programs at once, Mac OS X will swap the memory occupied by idle applications to hard disk when the active applications have insufficient RAM to work with. This constant swapping of memory to slower hard disk ‘slows down’ your computer. Increasing the RAM of your Mac does not increase the speed of the machine, it just makes the computer swap lesser and run at its optimal best.
We recommend a minimum of 2G for general computer usage. You will need as much RAM as possible if you run ‘heavy duty’ programs such as virtualization software (VMWare Fusion, Parallels Desktop), Photoshop, Aperture, digital audio video editing programs etc.
Buying RAM from Apple Store is notoriously expensive compare to compatible RAM that you can get elsewhere. For example the 4G memory kit (2x2GB SO-DIMMs 667MHz DDR2 PC2-5300) for MacBook Pro from Apple Store is $400. Compatible RAM from Crucial for the same 4G memory costs $104. We have been using compatible RAM on our Macs for quite sometimes with no problems whatsoever and do-it-yourself upgrading of RAM on your Mac is easy.