It does scaling well for apps which have been updated to fully support the UWP scaling APIs. Everything else is quite disappointing and wildly inconsistent. In my business, apps which use the UWP account for maybe 15% of usage time? I've encountered many situations where one cannot even achieve clear text, at any size, for a given app without overriding the default scaling system and using the "not recommended" custom scaling factor (i.e. the legacy controls).

Multiple monitor support on Windows 10 I've also found to be very dependent on your graphics drivers and hardware configuration, as it always has been.