I don't think I'll preorder with T-Mobile tonight after all. I think I'm gonna wait it out for the unlocked version from Best Buy (or Samsung themselves? Why aren't they also selling the unlocked version?).
I trust they'll keep up with monthly security updates per their recent promise for the unlocked models. The unlocked S7 just got march security updates, so that's a good start to their new promise. As for getting android O, I understand the android landscape; I won't knock them for being late on that. Besides, touchwiz on top of Android N is so feature-rich and, I presume, good that I'm really not worried about the next android version.
An opportunity to get Samsung hardware unlocked and bloatware-free only a couple of weeks after launch is too good of an offer. I rather not be tied to T-Mobile for anything. And getting it unlocked means I can sell it off later should something else I want come along later this year.
I won't be an early adopter this time, but I very much look forward to the unlocked version.
Overall, I think the S8 is a stunning release and an amazing next-step for not just the galaxy S series, but for smartphones as a whole. Kudos to what Samsung has shown today, and to how far they've come. They continue to improve and flex their hardware and software prowess. It's great someone is pushing the envelope.