I bought a Xiaomi Mi 9, it's a really nice phone. Although it doesn't have a 3.5mm and SD-card slot the rest of the upsides make up for it.
Initial impression is good, everything works as promised although MIUI needs getting accustomed to.
Update: After using it for a few months I am not really complaining, everything I need works nicely and MIUI hasn't generally been an obstacle. The only time I've been annoyed so far was when MIUI blocked bulk contact deletion, very stupid "feature".
I also tested out the dual-frequency GNSS, works nicely I can pick up GPS, GALILEO and GLONASS on both bands. However there seems to be no SBAS support on the Xiaomi Mi 9 even though the Snapdragon 855 should support it, maybe it'll get added but looking at how it wasn't promised then I somewhat doubt it unless someone hacks it together. Turns out that they're not always visible, the SBAS satellites. The Mi 9 has SBAS support and it works nicely.
The under-screen fingerprint scanner works nicely, just as good if not better than what I've seen on other phones. I wouldn't trade it for front-button or back scanner, it's IMHO easier to scan your finger using the front side you're using your phone with anyways.