I use Fedora, basically as it comes out of the box, with only a couple of Gnome shell extensions to make it nicer. My computer is a ThinkPad X230.
- I've never tried external monitors, so I can't say anything either way about that one.
- Printers/CUPS: always worked flawlessly (except for one single HP printer that just wouldn't). Autodiscovered network printers, USB printers, network printers have all "just worked" without an issue. I don't print that much though.
- Suspend/hibernate: I always suspend my laptop when I don't use it. That has worked flawlessly every time without any power management issues, sleep/wakeup issues or anything to complain about. I haven't tried hibernating though.
- Mounting USB sticks/drives: Never had a single issue relating to this. Every single time has worked flawlessly, exactly the same way: plug in USB, open it in the file manager, do things, eject, unplug USB. With both FAT32, NTFS and ext4 file systems, on USB drives, external hard drives, and SD cards.
- I've done two OS upgrades on this (Fedora 23 -> 24 -> 25) the normal upgrade way. Not a single thing broke in either of the upgrades. Both times the upgrade went literally like: start the OS upgrade, reboot to install upgrade, reboot after upgrade is finished, continue using computer without any problems. (By the way, Fedora 24 was the one that made Wayland good for use as daily driver for me, and 25 was where they made it the default.)
I realize that my comment is the definition of anecdotal evidence, and I understand that there are laptops with less fortunate hardware (Nvidia, some WiFi cards, some CPUs, etc.). But what I've realized during this year is that if they have a laptop with good hardware, then the common computer user can just install Fedora on their computer and get the same experience that I had, and that means Fedora is indeed in a very good place among the various desktop operating systems on offer today.