Don't like them, as they invent the wheel and try to teach new controls, although there are already tools built in to the system, so I just don't notice actually.
On PC I use Home button, scroll bar and, as mentioned in another comment, tap to the top of the screen on ios
I use the built in function of my android Samsung browser. On mobile it's a pain to scroll up after a longer read.
But. Whenever there is a href to main page somewhere, like fixed website header, that not only does reload the page, but also reposition the view to the page's "top" - I use that, because it lets me do two things at once.
The "to the top" appearing on Desktop browsers, I never use for simple reasons:
I have a mouse wheel and the other hand free for shortcuts or for changing the the scroll modus (Ctrl + wheel?) to fast scroll or just pressing the Home button.
.. also, the settings in Firefox have been modified to high values, to be very fast when Ctrl is pressed and using the mouse wheel, so I have less whole mouse movements.
That's the part that drive me nuts on Desktop. I don't want to move my entire mouse to a position, aim on the small element and move back afterwards, because I like to use the scroll bars :)
Whenever I see such function on desktop, I automatically ignore it.
On PC I use Home button, scroll bar and, as mentioned in another comment, tap to the top of the screen on ios