Your right the scaling quality of the skyQ box is excellent
Oddly there are several people on the Sky forums moaning that the upscaling from the Q box is "soft" and not as "sharp" as 1080p upscaled by their TVs.
I can only assume these people have their TVs adding loads of sharpening to upscaled 1080 sources which is making a native 4K source look "soft" by comparison. That's all I can think would explain it. Wouldn't surprise me if the (frankly awful) default settings on most TVs were doing this and still in use by many people.