First moan is if you want to replace XP or Vista (remember those $40 liscenses?). Not all hardware or software plays with W8.
Second moan is you need a Microsoft Account and are required to download many programs from the Microsoft Store.
Third moan, is, if there are problems or difficulties W7, is easy to troubleshoot, and find and identify what things are. Aps? Tiles? Not optimized for mouse and keyboard?
Fourth is that stupid hidden control bar, which does not function well with some old hardware. And can be annoying when the mouse loses it on any hardware.
Fifth the jump from W8 to w8.1 can mess with settings, programs, and defaults.
Sixth, Microsoft seems more interested in "look what we have" than simple usability, a year and a half after introduction, finding solutions can be frustrating, and sometimes impossible.
Seventh is ending W7.