iOS Safari support has been improved so that audio will be received even in some difficult network scenarios that were previously blocking traffic. iOS is still "listen only" due to lack of standards support in the Safari browser.
Support for Safari on OS X has been discontinued because OS X users may run either Chrome or Firefox for full support.
If you would like to see full support in Safari and on iOS, please send Apple your feedback and ask them to support WebRTC in Safari.
More information is available in the System Requirements.