As a general rule, updating your software or operating system or anything at all tends to happen on as-needed basis or at the very least "wait a few patches". You rarely - if ever - want to update right after a huge new version has been released.

The reasoning tends to go like this: You never know what's gonna stop working, because you never know who is on board with all the new updates. Some developers, like Native Instruments, will be able to verify that all their software is compatible (though some hardware will no longer work if you update, because they no longer provide patches). Others, like Universal Audio, cannot update their hardware and software so quickly and advised against updating.

I updated, and while I enjoy Sierra, I had a hassle getting my system up and running. I needed to go into the recovery mode command line access and disable certain features to be able to correctly reinstall the UA drivers in Sierra, and a number of my (thankfully freeware) plugins from Plugin Alliance and Izotope stopped working. I would suggest waiting if you're really interested in updating until all your third party plugin providers have verified they're ready. If you have a lot of outboard gear, do not update!!! It's probably not worth it.