Do I need more RAM?

Are you showing any page outs in activity monitor?

And I noticed a distinct difference in how my late '11 17" performs in going from 4 to 16 gigs. For under $100, definitely worth it!

 

To determine if you can benefit from more RAM, launch Activity Monitor and click the System Memory tab at the bottom to check your page outs. Page outs are cumulative since your last restart, so the best way to check is to restart your computer and track page outs under your normal workload (the apps, browser pages and documents you normally would have open). If your page outs are significant (say 1GB or more) under normal use, you may benefit from more RAM. If your page outs are zero or very low during normal use, you probably won't see any performance improvement from adding RAM.

Mac OS X: Reading system memory usage in Activity Monitor

 

Use the computer for a few hours. After those hours have passed, open up Activity Monitor, and take a screen shot of what you see, including the bottom details.

Be prepared to provide information about how long you have been running the computer since its last restart, as well as which programs you had been running during that time period. Use the computer as you would normally intend to.

Then we might be able to help.

 

Not necessarily. If you're having performance issues, this may help:

Performance Tips For Mac OS X​

 

Check your ram usage

Hey there, when you notice it going slow you should open up activity monitor and select the system memory tab. If you have hardly any free memory (indicated by green) you probably need more ram. You can also use activity monitor to see what is using all your ram by selecting the 'Real mem' filter in this window.

Here's a good tutorial on checking ram usage and how to buy the right ram: http://www.youtube.com/watch?v=ed2MvAyI66Q&feature=plcp

Hope this helps.

 

Doubling to 8GB is very cheap these days.

Honestly, the slowdown could be any of a number of factors including a slow disk drive, lack of RAM, or just poorly written software.