To remove just the icon at the bottom of your screen is not that difficult.
Disabling the Windows 10 Upgrade Notification
You can block the icon from showing and disable notifications. Using the Windows registry editor, do this:
Navigate to: HKEY_LOCAL_MACHINE \SOFTWARE\Policies\Microsoft\Windows\Gwx
Create a new REG_DWORD registry value called: DisableGwx
Give it a value of: 1
For many users, if their Windows 7 or 8 is working fine, I would not upgrade. Windows 10 is probably a good thing but give it some time to allow them to work out all of the bugs, which are always present. The free Windows 10 offer is good for a year and I will probably upgrade near the end of the year.