This upgrade brings the Keep app up to version 3.1.294.00, and so far it seems this may be the only significant change in the interface. For those who may not know what we are talking about, the floating action button is that bubble you often see in the lower-right corner of some Google apps. It’s usually a shortcut for starting a message, reaching contacts and other handy tasks.
As it goes with these OTA updates, Google should be rolling out the improvements periodically. If you don’t see the update show up in the Google Play Store, just wait for it, it'll come eventually.
[Source: Android Central]