I have a feeling this won't be the release version on September 30, hence the "Candidate" word at the end. On the side note, the GM for iOS 9 would most likely be the same as the release version since it was released so close to September 16.
I'm quite sure this is the final build.
The 10.11 GM candidate installer was built on a later build, and there will be a release build that, if nothing else, unifies the developer and public betas.I'm quite sure this is the final build.
When it comes to beta, I interpret stable as being relatively free from constant crashes and reboots. Just because you experienced a panic in a specific situation with several variables, that doesn't mean that other people using the OS differently will experience the same.
From what I have seen on the forum, (as a whole) El Capitan has been stable for most users who have taken the time to respond.
The poster was talking about Yosemite.What utter rubbish your POV is. El Capitan is probably the most stable OS since 10.6. Just because your shambles of a computer had problems is not our fault.