This drives some of our customers nuts because autocomplete has the annoying tendency in the most recent Safari of overwriting prepopulated fields - users end up losing configurations over this.
Otherwise I can see the benefit of ignoring the setting, perhaps, but we need consistent default behavior (chance would be a fine thing!). I don't want to be telling my customers that they should switch off autocomplete as a user shouldn't need to configure a browser to use a website!
Have you filed a bug report about Safari overwriting prepopulated fields? If not, and you don't want to deal with the painful experience that is bugreport.apple.com, feel free to drop me an email with more details about what you're seeing.
Otherwise I can see the benefit of ignoring the setting, perhaps, but we need consistent default behavior (chance would be a fine thing!). I don't want to be telling my customers that they should switch off autocomplete as a user shouldn't need to configure a browser to use a website!