Only open combat on the Internet will let us know how well Swift's security model works, but it is likely an improvement over Objective-C and could, over time, help harden app security in both OS X and iOS.
Safari gains more usable privacy by allowing users to open a private browsing window without flipping the entire browser into private mode. This is the same as Google Chrome's Incognito model, which is much easier to use than Safari's current on-or-off model. I'm also curious as to how deep the privacy restrictions run; those pesky Web advertisers are quite devious at circumventing most privacy controls.
On a lesser note, I'm thrilled that we will soon be able to use the privacy-conscious DuckDuckGo search engine right from within the address bar. It's a nice touch for the privacy-minded.
Apple didn't mention anything more on OS X security and privacy, but every other version of the Mac OS has added a variety of unpublicized security and privacy controls. With months to hunt them out, I expect to find more.
iOS 8 and Yosemite appear to be less about adding new security and privacy features, and more about opening and extending them deeper into the app ecosystem. The more Apple enables security for developers--not just for the operating systems themselves--the better our devices will be able to withstand the dark side of the Internet.
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