Rating System*:

Five Dunnies - You might well find this toilet in your own home. Odor quickly disapates, cleanliness is a given, supplies are present. Entrance is never questionable.
Four Dunnies - Sharing most of the same qualities as a fiver, a four might be in a less desirable or convenient location (i.e. - up a long flight of stairs or across a busy highway).
Three Dunnies - Filling the midpoint, three is a nebulous rating. Privacy and usability are present, but other elements are missing such as a seat, or pleasant environment.
Two Dunnies - You have landed in a place where shoes are considered the filthiest things on the planet - and for good reason. Wash your hands elsewhere.
One Dunny - How bad do you really need to go? Using a one requires a level of desperation usually reserved for a few hours after big meal in a 3rd world country. Consider suicide as an alternative.

*rating system on a sliding scale relative to location.