Lot of fixes to packaging, code and documentation have been committed since RC1, Kamailio 3.0.0-RC3 becoming ready for pre-production phase.
If you like to work with source, then use the tutorial guiding the installation of Kamailio 3.0 branch from GIT repository:
Two wiki pages were created to collect what is new in Kamailio 3.0 and how to migrate to this version:
Feel free to contribute to wiki pages, helping to build migration tutorials.
This is the last RC before full 3.0.0 relase. Please report any issue you find to sr-dev at lists.sip-router.org.