I'm having the same decision struggles as others here.
My wife and I are on AT&T Next Every Year, and have upgraded iPhones every year since 2007. We have the X, and for the first time I can definitely say that this iPhone is such a great phone in every respect that it leaves me wanting nothing. I have zero complaints about the design, speed, screen quality, photo quality, etc. In past iPhone generations, there was always at least one thing I wish was better. Not any more. This makes it hard to decide whether the upgrade is worth it.
The Xs is clearly improved in a number of ways. The question is, are the improvements enough to make the upgrade worth it?
We don't play intense games on our phones, so all the CPU/GPU improvements aren't that important, especially given how fast the X already is. FaceID speed improvements sound great, but not sure how much faster it really is. We do take a lot of pics and videos and are photography buffs, so the camera improvements are compelling, but we don't have real-world testing data yet until the reviews hit. So it's hard to say how well those improvements translate in real-life use. If they are significant improvements, then it is probably worth it to us.
Sure, we're already on Next, so we can upgrade without paying any more than we already are, and that's the habit we got into a long time ago. But if we didn't upgrade, then the phones we have now would be paid off in 12 more months, we'd then own the phones, and they'd be worth (I figure) about $450 each on eBay (times two phones). That resale value essentially offsets the payments we would make over the next year. So there is a big financial advantage to holding off. But I'd pay a convenience penalty by having to then deal with selling them on eBay. We switched to Next so that we wouldn't have to do that anymore. Though, I ran into extreme difficulties with AT&T last year over a returned phone that they had no record of receiving, so there's that too. At least I know how to deal with that if it comes up again (email the CEO email address-it worked like magic).
This would be easier if I could just see how big the camera improvements really are.
I'll likely go through with the preorder, knowing that I can read the reviews when they come out and cancel if we change our minds.