Faster Flex Builder Compile Time

To increase Flex Builder compile time during development, the following tweak helped my Flex 3 builder to go from 30 seconds to just a few seconds for a medium sized project.
Open project property, under Flex Compiler -> Additional compiler arguments, add " -incremental -keep-generated-actionscript"

It definitely helps me go from compile once every hour, to every few minutes. Such that I can get immediate feedback through compiler errors or warnings.

file 'lib' not found

When installing Ruby on Rails using command: gem install rails
Got this error message: file 'lib' not found
Seems like it's fixed by running gem instal rdoc followed by gem install rails again.