Will 'back to top' links/buttons make my site more usable or just be noise on the page?

I have never understood those links since I started using the web (around 97). I have no idea why clicking that link would be faster than using the 'Home' key. I don't know why it would be easier than clicking on the scrollbar. The worst thing: Since every site is a bit different, you always have to search for these links before you can use them. Even if that takes just one extra second or so, it's simply not worth it.

The only variation that I could maybe understand would be if the link used "fixed" positioning, so once you know where it is (on a site that you visit regularly), you can already put your mouse pointer there while you read and scroll the page. But I really don't see how a "back to top" link provides any convenience when it scrolls with the page content.

I actually believe that the link became popular because it has always been used as an example in many HTML tutorials, as it's an easy way to explain anchors. I'm not sure if the tutorial authors ever meant that these links are really a great idea. (When you think about it: Wouldn't it make more sense if every browser simply showed a "back to top" button e. g. in the status bar - at least for long pages? And if you don't like it, you can turn it off.)

If the page is long, or very segmented (like an FAQ might be) a back to top link can be a very handy feature and improve the usability of your website. If you're putting them on your page just because you feel like it then just like any extraneous content/features it's just noise.

Always do something with a purpose. Not just because you can. (A common mistake newer developers make is to do something just because they learned about it recently, not because their project actually needed it).

As far as where to put them, where do you think they would be useful? In the case of an FAQ the would be useful next to each question. They should be obvious and consistently positioned.