If you have no intention of getting the free Windows 10 you can remove "that ubiquitous windows symbol offering a free upgrade to Windows 10 that has appeared on the notification area", by going to, (in Windows 7), "Control Panel" then "System & Security" in "Windows Update" select "View Installed Updates".
In the list of updates search for update KB3035533. Right click on this update and select "uninstall". Restart your computer and the icon will have disappeared. To stop the update installing again you will need to go back to Windows Update" and select "Check for Updates". The offending update will now appear in the list of available updates. Right click on it and select "Hide". It will now be gone. Of course if your PC is set to automatically check and install updates it will return. For those with Windows 8-8.1 the same thing applies but it may be a slightly different process to get to "View installed updates" via "Control Panel".
Should you change your mind at a later date you can go back to Windows Updates and "Restore Hidden Updates" and reinstall update KB3035583.
If you do reserve Win 10 it will be downloaded to your machine after 29th July.
https://www.microsoft.com/en-gb/windows/windows-10-upgrade
You can then finally decide if you want to installed it or not. If not, just delete the download.
I intend to follow SlackAlice's advice and see what others say who are using Win 10.