For those of us who wanted a bigger iPhone and the best possible display Apple offers, this is the best we could have had. The display is an 6.5 inches OLED screen and everything looks really beautiful on this screen from videos to photos. The phone is really big though so unless you have big hands, it might be a good idea to go to an Apple store and try it before buying it.
The downside is that not all the apps are optimized for the screen yet but for those that do, like Whatsapp for instance, everything looks better on the gigantic screen and the situation is getting better since the phone has been out for more than a month now.
The modem is now made from Intel instead of Qualcomm. I didn't personnaly experience any difference performance-wise on LTE and on Wi-Fi, I'm having the same numbers as on my iphone X.
Some people experienced network issues in the beginning. Those issues are easily solved with a network settings reset.
I'm a big fan of the jack port but I think that there's no way Apple is going to put them back on the iPhone. The problem here is that they don't include the little dongle anymore so if you have wired earphones, you have to buy one for 10€/$.
The build quality is there as you'd expect from Apple and the phone is now IP68 instead of IP67 which offers better resistance to dust and water. I can't afford to make drop test so I won't be able to tell for the durability but I can feel that it's solidly build but that was true of the iPhone X already.
The camera offers a nice upgrade compared to the previous one found in the iPhone X. The photos are better specially in low light and they offer a better HDR. The portrait mode with the ability to tweak the aperture after the photo has been taken is a nice addition. It's a shame that this feature is limited to the iPhone Xs's only. Some third-party apps offer that possibility on older models. That's the Apple doing I personally don't like at all.
I won't be talking about IOS and the ecosystem since it's mainly the same experience that is to be found on an iPhone except for the home-button iPhones that don't have all the gestures that have been introduced since the iPhone X.
To summarize, if you are looking for a bigger iPhone with a better camera, better battery and the latest and fastest experience on IOS, look no further, the iPhone XS Max is the way to go.