Disadvantages
cross domain issues
can’t create signed RSLs
debugging
quick editing
must download the whole RSL (doesn’t trim unused classes)

RSLs act like diet pills for the size.

What is an RSL
Purpose
To quickly reduce your apps file size
code one, use in many places
How do it do that?
Kung Fu.
separates large code of flex into other places

Terms
RSL – runtime shared library
Signed RSL – Adobe published RSL
Unsigned RSL – the RSL for the rest of us
SWZ – an adobe signed RSL
SWC – zip file contains compiled Flash/Flex project that is not standalone code
Library.swf – one of the two files that are in a SWC
Catalog.xml – second file in a SWC
Compc – component compiler
Browser cache – your browsers of choice cache, not to be confused with Flash Player Cache
Flash cache – Flash Player’s internal cache
ANT automated command line built utility

Where do I find my RSLs
SDK/frameworks/rsls

Flex Core RSLs
how to speed up your apps? make the file size smaller.
1. use case: app is big. too big. you need it smaller and faster.
solution: separate your flex framework from your RSLs
2. use case: you have a project that has a core set of components, libraries, or utilities that are pretty much stable and you dont want to force the users to re-download all of that every time on release.
solution: create an RSL
3. use case: you, a friend, a co-worker or some dude in India just gave you a SWC and you want to use it as an RSL
solution: import into your project and make it an RSL
4. use case: your company has a common set of components, libraries, or assets that you want to share across multiple projects
solution: create a cross-domain RSL
digest must be enabled “-compute-digest=true”
5. use case: feeling good but client wants even faster!
solution: run the optimizer
6. collaborative work
7. automated builds for deploying RSLs

Something to laugh
http://www.youtube.com/watch?v=xUosP0Hkoek