Long read but some impressions using it awhile coming from the 7 Plus and Galaxy S8+ before that
A lot narrower than the 7+, will take some time getting used to if you're coming from a Plus or a 6" android. It's definitely an OLED screen but it's a lot closer to the LCD displays they've been using than a Samsung one, colors don't pop as much. If you don't like the unnatural Samsung displays then the screen is perfect, if you like those colors you'll be a little disappointed. I like Samsung's displays so I expected a little more saturation being OLED but Apple tuned it to what it's customers are used to seeing/sRGB so it's whatever. It's still a good display, I like skin tones on the X better than the S8+, everything else I gotta give to the S8/Note8. True Tone was the first thing I turned off. Instead of adapting to my surroundings, it made my display yellow in all conditions. shyt is trash.
Face ID is about a second slower to unlock the phone than a fingerprint from what I can tell, won't even be an issue this time next week. I like it a lot more than Samsung's offerings, the iris scanner always made my eyes feel weird after using it because I'm pointing a laser directly in my eyes. There's a health warning when you set it up for the correct distance to use it at but it's so finicky that you end up having to hold it in your face in an unnatural way to use it. There's a little more leeway with FaceID, less having to feel like I'm posing for a selfie just to unlock my phone and more of just looking at it. Blurring notifications unless I'm the one unlocking the phone and even changing Face ID so that it can only be unlocked when I make eye contact with it instead of just pointing it at my face is just better than what Samsung has out of the box.
I didn't even notice the notch going through the setup menus, screen just wraps around and buries it. Apps will have to be optimized and all video will be cut out around it for sure, might be a dealbreaker for some but I think a lot of the hysteria was overblown. I don't see it being an eyesore like some people want it to be.
Haven't fukked with the camera yet. Other than double OIS shouldn't be too different than the 8+ which isn't too different than the 7+.
Best iPhone so far imo, only way it wouldn't be worth the upgrade is if you fukked up and got a 8/8+. I wanted a smaller phone the Galaxy S8+/7+ and I like how they did the bezel-less display. I preferred the infinity display at first but there isn't any distortion from curved edges on the iPhone so I guess I like it more. Physical feel of the phone feels like this year's Galaxy phones, smooth and slick the whole way round with the glass back and treated metal. They're even the same phones when it comes to the facial unlocking/security features with Apple's being a little better imo. And I told you the silver one was the one to get but the grey has grown on me a little. It's just missing little details that the polish on the silver brings out without looking cheap or tacky.
Long story short: It's a Galaxy phone running iOS. If you never liked iOS it isn't for you, if you do, since is Apple looking at LG making the display next year the iPX is the closest we'll get to having the best of both worlds.