After being released for the Samsung Galaxy S8 on Verizon last week, the Android Oreo update is now rolling out to S8 and S8+ owners over at T-Mobile. The updates bring the latest version of Android as well as the February Android Security Update patch to the 2017 flagship devices.
For those of you who have the Galaxy S8, you are looking for build G950USQU2CRB9 while those of you who have the S8+, you are getting build G955USQU2CRB9. Both updates come in at just over 1.5GB in size so you will certainly want to download them via WiFi when you get the notification of it being available. As of now, T-Mobile has not updated the support pages for the devices to reflect the new build release notes.
As for what you are getting, the most noticeable change beyond the goodies that Oreo itself brings is the new Samsung Experience 9 user experience. This is the same experience of the new Galaxy S9 and brings things like improvements to edge panels, new clock styles, and an always-on display. Experience 9 also brings some improved stability to the device as well as some performance improvements as Samsung did a fair amount of work on it in preparation for the S9. You, as a S8 owner, get the same benefits.
The update for the Samsung Galaxy S8 and S8+ on T-Mobile has just now started rolling out so it could be several days before everyone sees it on their devices. If you want to manually check for the update, you can do so by going to Settings>Software Update.