Flex Builder 2 is great and powerful IDE for developing Flex applications.
If you use the tool as Eclipse plug in (but it's the same for the stand alone version), you'd note that it requires a lot of resources to work !
In fact the performance of Eclipse seems to progressively decrease as the number of your MXML and Actionscript files grows in your projects.
I found three useful settings to maximize Flex Builder 2 performance :
- closing all the projects you don't need (right click on them an choose Close Project)
- unchecking Enable Code Folding under Window > Preferences > Flex > Editor
- increasing Eclipse's startup min max memory settings using the in the file eclipse.ini (the settings you have to increase are -Xms40m and -Xmx256m)