I have noticed some S8 handsets do actually have concave rear panels. It is very very slight, barely noticeable to the naked eye. The only way I've tested it is with a small ball bearing. The bearing would always roll directly to the center of the rear panel. Because of this, the phone sometimes builds up an air cushion, making it slide like an air-hockey puck. A case for these phones is an absolute must! They are 95% made up of extremely fragile glass, probably intentionally. If Samsung refuses warranty, and offers service, do your best to decline, and check out a local third party repair store. Rather give local business a chance over Samsung!
Thanks Bogdan for your riveting reply. The glass isn't easy to remove on its own, but it is possible. It is much easier once you've gutted the phone, as you can bend and twist the frame ever-so-slightly to loosen the adhesive on the device without compromising the LCD. The phone definitely performs well, but its build quality might be a little bit underwhelming to anyone with an eye for that sort of stuff. For the average consumer, eh, who cares about a bit of lag?
From memory, (did a teardown just recently,) the S8 Battery is significantly heavier than an S7 battery. It is quite a bit thinner however, so the added weight must be caused by the internals. I'm no expert on battery composition but I know for sure that S8 batteries are much more durable from a repairers point-of-view.
There is no seal on the screw. The head of the screw simply pushes against the lip of the screw well, without using any sort of pneumatic seal, o-ring etc.
As Talon says, it is part of the casing.
Great guide, very accurate. Be very careful along the right side of the device, as it is very, very easy to shear the connector flex in half. To avoid any chance of damage, I remove the board and front camera/sensor flex. It's an easy job, and saves a massive headache if any parts are damaged. Overall quite a familiar phone to work on, if you've ever done any S6's and upwards.
Heat guns are much more efficient as there is a considerable amount of glue throughout the middle of the phone. Would recommend using a heat gun over the iOpener.