Few issues with the S8 Plus, user error mostly.
S7 Edge, would randomly corrupt my SD Card. However the S7 made it seemless when transferring apps and files from the internal memory to the external memory.
S8 Plus... same thing. Except they convoluted the menus and you can't find the transfer feature, you gotta dig for it. The search option in the settings is useless.
I just bought an ATA 128GB 85 mb/s Class 10 SD card. I had an old Kingston 32GB SD (definitely had its run) so we'll see. I couldn't find a Samsung EVO 128GB because they were out of stock, and the 256GB was really expensive... I might return this and go for the 256GB we'll see or wait for the 128GB.
Apart from the SD card issues, which are mostly user failures, the durability of the AMOLED hasn't increased that much.
I've had the phone for about 6 months now and already I have screen burn-in. Again, user error, I slept with my WhatsApp chat open and I had left my hand on the screen... overheating the phone and causing the burn.
Not too bad though, considering the S7 Edge had a much more severe burn.
Overall though, it's a great phone, camera is great.