New macOS Sierra 10.1 beta available for registered developers
Apple is continuing apace with developer betas, and has made available a new developer beta of macOS 10.12.1 to eligible participants.

Build 16B2333a of macOS 10.12.1 Sierra is now available for registered developers to download, either through software update or through Apple's developer portal. Sierra now includes support for the iOS 10.1 beta "Depth Effect" feature in the included Photos app.
Apple has not identified any particular foci for testers in this build, nor has it posted any bug fixes over the previous beta.
iOS 10.0.1, watchOS 3 and tvOS 10 were released publicly on Sept. 13.. macOS 10.12 Sierra launched to the public a week later, on Sept. 20..
Members of Apple's public beta program are likely to receive similar beta builds of macOS Sierra 10.12.1 in the coming days. Apple excludes watchOS, tvOS and Xcode from public beta tests.

Build 16B2333a of macOS 10.12.1 Sierra is now available for registered developers to download, either through software update or through Apple's developer portal. Sierra now includes support for the iOS 10.1 beta "Depth Effect" feature in the included Photos app.
Apple has not identified any particular foci for testers in this build, nor has it posted any bug fixes over the previous beta.
iOS 10.0.1, watchOS 3 and tvOS 10 were released publicly on Sept. 13.. macOS 10.12 Sierra launched to the public a week later, on Sept. 20..
Members of Apple's public beta program are likely to receive similar beta builds of macOS Sierra 10.12.1 in the coming days. Apple excludes watchOS, tvOS and Xcode from public beta tests.
Comments
This is the first release of macOS I regret jumping on. Here's to hoping the point releases are significant
This has been reported for days. What's doing the slowing down and Activity Monitor spikes is Sierra indexing. I noticed with iStats that I use the CPU was running very fast. Give it some time and depending on what year of your mac and how much storage you have used, it could take awhile. Once the indexing is done, do a reboot too. Btw, the cause was mainly Photos. With my iMac and it's a recent 5K, it still took some time to index. Hope it helps.
https://discussions.apple.com/thread/7676728?start=0&tstart=0
Hiwever installinnghte first minor update hasn't been all that wonderful with a few glitches here and there. Nothing major but frustrating nine the less.