The biggest disappointment for me is that Touch ID is no longer in the phone, yet we all fully expect it to be in the next one.
Therefore, when we're all there slinging our iPhone X's in 2019, we'll all be receiving comments like, "Oh yeah, that's the one they released without TouchID isn't it?" and that just doesn't sit right with me.
TouchID is more convenient. Although I've never had it (iPhone 5 user), I still have used it and have always wanted it. The screen and camera improvements mean that I'll still get the X, but I was hoping to wait another 5 years before updating. Without TouchID, I can see myself wanting to update sooner, which isn't a good investment vs upgrading every five years.
I can see FaceID getting tiresome quickly.