• the UI may be noticeably slower on some systems
• it is more difficult to avoid using a Microsoft account
• the task bar cannot be moved and customization is more limited
• some right click menu options are hidden behind an extra click
• the start menu is different. More like an app drawer than previous versions.
• some long depreciated features (like ungrouping taskbar items) were removed.

Personally none of that bothers me, but everyone’s usage is different.