Earlier this week, Samsung said that the update would be rolling out within 2 to 3 weeks, so it looks as though AT&T and Verizon decided to jump the gun (not that we're complaining). It remains to be seen if T-Mobile and Sprint will decide to step up their release schedule as well to match their larger rivals, or allow more time for testing before pushing Android Oreo out to customers.
As for those with unlocked versions of the Galaxy S8, Galaxy S8+ and Galaxy Note 8, you will probably have to wait a bit longer, unfortunately:
[You] may be wondering why those with Carrier models are seeing the updates first. The reason for this is that Unlocked devices must go through more rigorous testing than Carrier-specific devices because we need to make sure there is proper network functionality across ALL supported networks. (Ex. Carrier-specific devices are made to handle that one network. Unlocked devices need to be able to handle ANY / ALL compatible networks. Thus, they require some more preparation.)
To see if the update is currently available on your Galaxy Note 8, you can manually check by navigating to Settings --> Software Update --> Check for Updates. If you're a Verizon or AT&T subscriber, and you don't see the update, you just may not yet be in queue to receive it at this moment. So be patient, and it will eventually find it way to you.
The Android Oreo update for the Galaxy Note 8 (like the version available for the Galaxy S8 and Galaxy S8+) includes the Samsung Experience 9.0 UI and Google's most recent Android security updates for March.