Teo Yu Siang in a great post on Medium:
FABs are circular buttons that float above the UI and are “used for a promoted action,” according to Google. They act as call to action buttons, meant to represent the single action users perform the most on that particular screen.
And because of the bold visual style of Material Design, FABs are strikingly hard to ignore and stand out — and herein lies the problem.
While FABs seem to provide good UX in ideal conditions, in actual practice, widespread adoption of FABs might be detrimental to the overall UX of the app. Here are some reasons why.
Material Design is an exciting direction for Google, but I have a hard time getting past some of the usability concerns with it.Written on June 3rd , 2015