1. The performance is bad compared to Smoothwheel. (You cant make it fast and smooth at the same time.)
2. Does not work on all web sites. SmoothWheel always worked perfectly.
3. Needs the ability to scroll in fractions of a page - e.g. 1/2 page, 1 page or 9/10 page, etc. (like SmoothWheel)

https://web.archive.org/web/20160514131813im_/https://addons.cdn.mozilla.net/user-media/previews/thumbs/1/1011.png?modified=1331218902

While this add-on works, it really sucks compared to Smoothwheel. That was the best -- it was smoother than anything else, it had better controls, it worked on all web sites, and it worked with all mice (until Firefox Quantum broke compatibility.) Someone needs to resurrect this extension. I hate Firefox without it.

https://web.archive.org/web/20161123223319/https://addons.mozilla.org/en-US/firefox/addon/smoothwheel/

http://forums.mozillazine.org/viewtopic.php?f=38&t=3033273
http://smoothwheel.mozdev.org/