The City Pilllar Shrine is lovely, but both for tourists and for devotees not from Bangkok, it is - in the best sense of the word - a secondary attraction. So, this is a great, relatively briefly-visited destination for those who have been in Bangkok a few times already and have seen the palace, Wat Pho, and the National Museum, just to talk abut the immediate neighborhood (which is somewhat stern, barren, and unforgiving).
The spiritual meaning of the pillars, as well as the other sanctuaries, are not easily understood by outsiders (much less than in a Buddhist what for instance), but it is a nice, very active place. The five Guardian Spirits include on the right Chao Chettakhup, in charge of bureaucracy and public administration. He is not often so accessible, and he also keeps the books of peoples' deeds upon which basis they are judged after death. Anyone with an issue with Thai or other bureaucracy may find it worthwile to make a little merit here...