Hey guys, just had it for a few hours. T-Mobile 512gb, Ocean Blue. Previous phone: T-Mobile Note 8.
1) Definitely notice the slight weight increase and slightly boxier form. Feels real good.
2) Screen is cooler than my note 8. My note 8 had a perfect screen from everything i could tell but having them side by side with same "adaptive display" and in the same lighting, the Note 8 has a reddish hue and the Note 9 just looks cool white/blue which i vastly prefer to a warm display. This can obviously be changed in settings so not a big deal.
3) Never turned on "Download Booster" on my Note 8 and decided to flip it on for Note 9. Then started downloading a bunch of apps. In-SANE! PUBG (1.6gb) downloaded in under a minute I think, not sure. Of course in Atlanta, I get T-Mobile speeds of 100-180mbs down regularly and my wifi is 300mb Comcast, but still. Was an incredible difference to Note 8. Also, as fast as I was clicking apps to download, the previous one was done. That has never happened in any high smartphone I've ever had before.
4) Fingerprint Scanner change is a small thing but huge improvement for my smallish hands. I know most reviewers are pretty "meh" about it but I would say it's a very nice change. (I never got around to owning the S9 or S9+)
5) random, but S-Pen clicker top seems slightly less solid than on Note 8
6) Only listened to a few videos and not a fan of the weird speakers. Would have been much better if both front facing. The bottom firing seems quite a bit louder than the earpiece speaker and it just sounds uneven when you are trying to listen. Definitely much louder than the Note 8 and i'm sure i'll get used to it soon though. Just annoying enough to comment on though.
Ok that's it i'm sure i'll have more. It was a little anti-climactic opening it today since I had the Note 8 and they are basically twinsies but i'm glad to have the ultimate Swiss Army Knife phone now and the improvements over Note 8 are substantial (much faster CPU, stereo speakers, more network bands, tons of storage, better camera, s-pen tricks, etc

Love it and won't be buying another phone until the Note 10 comes out in a year. Feels good after buying 4-8 phones a year up until the Note 8. Now just 1 a year but don't feel like I'm missing out on anything with this Note 9.