If you are running out of app space on your internal storage, then it could be very useful, but if you have a lot of space still available, then there is no point. It doesn't work with all apps as it depends on the whether or not the developer explicitly set the app not to be movable to the sd card. Remember that the sd card reads and writes more slowly than internal storage and is not mounted immediately upon boot up, so you may want to avoid moving apps that are set to run at boot time. Also, widgets, system apps, etc can not be moved either.
This feature has been around since 2010 in Android 2.2 Froyo, though you may not have seen it on your past devices because it was up to the device manufacturer if they hid that feature in the settings or not.