By providing a temporary space for your file- and app-content drags,
Yoink frees up your mouse to let you navigate more freely and comfortably to the destination of your files. Yoink accepts any file from Finder, and app-content from almost any app.
Been using Yoink pretty much since it came out and have it has proved a very useful utility in my day-to-day work. Haven't used it on iOS yet though, as haven't really found the need for it yet, but maybe after the announcements from Apple later today… who knows?
It's just there for when you need it
None to speak of