Apple is seeding the third developer betas of iOS 11.1, watchOS 4.1, and tvOS 11.1 today, only a week after it released the second builds. Being the third build of minor updates, there's not a lot that's new.
The big new feature in iOS 11.1 is going to be the availability of hundreds of new emoji characters, which is part of Unicode 10.0. This particular build includes some fixes, and there's still a known issue that has to do with the unreleased iPhone X's front-facing camera. The rest of the issues seem to have to do with the developer end of things.
watchOS 4.1 beta 3 doesn't include any known issues at all. In fact, last week's one known issue has been fixed, which is that tapping the add button in Now Playing no longer prompts you to turn on iCloud Music Library.
The only notable known issue in tvOS 11.1 that on-screen brightness is increased with HDR output. The others, like Ethernet connectivity ceasing to function, have been fixed.
If you're waiting on this update to hit your device, you can always join the Apple Public Beta Program for all of them except watchOS. If betas aren't for you, it won't be more than a few weeks before they are released to the public.