Edge scrolling area is too thin on touchpads
When edge scrolling is turned on for a touchpad. It feels like as shown below.
It's not just me who finds this libinput behavior inconvenient and less usable. User comments on various forums confirm the weird and unnatural behavior. 
I might add that the edge is very thin though, really have to be at the edge of the touchpad.
Since you're deprecating the synaptics driver in favor of libinput, it would be vital to have at least the same features. Since you're not letting the user configure edge area in libinput, it would be vital to have at least synaptics' default setting for edge width.