Let’s see. . .
1. It fails to recognize “legacy” peripherals (like a year-old Epson Printer, or a current-generation Nvidia high-end video card.
2. All semblance of user control goes away. Windows will update as it sees fit, whether you want it to or not. Even if some of your software REQUIRES older drivers.
3. Win10 is a year or two away from being a Subscription. Want more than basic services ? Pay your monthly Microsoft bill. . .