May I assume that you did not have Artie's issue of disappearing passwords and keychain?
Not a bit of it in any of the numerous almost bi-weekly beta updates or in upgrading my wife's computer or our server.
FULL DISCLOSURE: My results may be colored by the fact my Keychain and Safari settings, autofill data, even my Desktop and Documents folders are on iCloud and shared by my MacBook Pro, iPhone, and iPad. It is possible those could be lost of overwritten in an upgrade or update, but I would never notice it because they would immediately be available and restored from iCloud as soon as I entered my Apple ID and password. (You wouldn't believe how easy that makes it to recover after a "nuke and pave" upgrade/update, disaster, or setting up a new device. The only thing missing are third party and app-store apps.)
