In the last couple of weeks I upgraded my MacBook Pro and iMac from 2 to 4 gigs of RAM. It cost me about $100 at Other World Computing for the 2- 2 gig sticks of RAM, so that was about $200. I checked just now and you can get out the door with UPS ground shipping for under $98 for 4 gigs of RAM for the MBP or iMac Core 2 duo machines.
I tried on my own to install the RAM and after encountering the slightest bit of difficulty in each case (a screw was too tight for me and I worried about stripping it), decided to just ask my local Marin Mac Shop to install the RAM. Their charge? $27/machine. Any questions?
If you operate towards the power user end of the spectrum and have relatively powerful hardware to match, RAM is so cheap right now that you would be foolish not to upgrade up to 4 gigs of RAM if you can. That gives you headroom for things like 25 tabs open at once in Safari plus maybe 10-20 open applications. Works for me!
Now I feel like I'm not handicapping my fast Macs. It's crazy to spend around $2500 for the Mac and then cripple it even a little with not enough memory.
I have to admit that both these machines were fast to begin with and I really didn't have any complaints at all about my new 2.8 ghz iMac. But, who knows what it is capable of if it is limited by RAM a lot of the time?