I am not sure what you would need a folder with 16 or more apps for. I don't know maybe you have a "Games" folder and you are obsessed with Android games and actually have more than 16 games, or maybe you have a bunch of business apps on your phone for work and you keep those neatly organized in a folder. You might find this new feature pretty usable if you are one of those who stores lots and lots of apps in a single folder. In android M you can scroll horizontally in your folders. Once you add more than 16 apps in a folder your folder automatically creates pages with 16 apps per page. Being able to scroll horizontally will make finding your apps easier and make the whole folder experience seem less cluttered. This is definitely a great new feature!