Apple today released a new build of macOS 10.12 Sierra to both developers and Public Beta testers. Developer Beta 8 and Public Beta 7 come with the build number 16A313a, and the news comes just a week after the last build was offered.
Most of what's new with today's seed include fixes and under-the-hood improvements, as the company is gearing up for a GM seed, which is likely to be offered following the iPhone event on September 7. Indeed, it's quite possible that this will be the last beta of macOS Sierra before the final version next week.
The release notes have about four pages of "notes and known issues". Of them, four list a workaround. Many of them aren't bugs; for example, the latest version of Xcode isn't compatible with macOS Sierra. You'll need to use the Xcode 8 beta.
Keep in mind that macOS 10.12 Sierra is the first version since OS X 10.8 Mountain Lion to not support devices that its predecessor did support. To install Apple's next OS, you'll need a MacBook or iMac from late 2009 or later, or a MacBook Air, MacBook Pro, Mac mini, or Mac Pro from 2010 or later.