I've had my X for 7 weeks now.
Dislikes:
1. FaceID doesn't work for me nearly as often as TouchID did on my 7+. As a result, it feels like I've manually entered my passcode more times in the past month than I did in the last year with my 7+.
2. The display is narrower than the 6+/7+/8+, so in landscape mode much content is letterboxed. Usable screen area is closer to that of an iPhone 8 than an iPhone 8+.
Likes:
1. The OLED screen is gorgeous.
2. I didn't dislike the bezels on my 7+ or earlier iPhones, but I am loving the absence of the top and bottom bezels on the X. (Side bezels on the X are the same as on other iPhones.)
3. The camera is noticeably improved over the 7+ I had before (which itself was pretty good). More natural colors and much better low light performance. Portrait mode is a bit better than on the 7+, and I love that you can get portrait mode on the front-facing camera.
4. Love the form factor. The size and weight are less than the 7+ I had before, making it nicer to use and more pocket-friendly. Yet the screen is bigger than the 7 or 8.
Neutral:
1. Battery life for me has averaged about 8 hours on the X, a step back from 10 on the 7+ but not bad given the smaller device size and the demands of the array of sensors in the "notch". Plus, some of this is iOS 11. Battery life has been highly variable for me across the various builds and betas of iOS 11. I thought that was setting down since 11.2, but the latest beta (11.2.5 b3) seems to deplete the battery a little quicker than other recent builds. Still, I imagine this will settle down and battery life will become more consistent, and sooner rather than later. (I hope.)
2. The notch. I don't hate it, don't love it. Sometimes I find it annoying when viewing something in full screen, especially in landscape mode. Other times I actually like the notch; it contains a bunch of new tech and therefore has a bit of a "cool factor." When people (who care about tech and don't have an X) see my phone, the notch immediately tips them off that it's an X and they ask how I like it, ask if they can hold it and play with it.
3. My love of the size and weight (being, to me, in the sweet spot between 8 and 8+) is offset by my mild unhappiness with the reduced usable screen area (in landscape mode).