Although most of my relatives are not covered in these census substitutes, others are. For example, Greenville, South Carolina is well represented in the city directories. Many of my SC ancestors moved here to work in the mills.
In the 1948 Greenville City directory I found my grandparents, Roy & Betty Huyler Albea. They had been married in Greenville in February of 1947. This directory shows my grandparents during their first year of marriage. Roy was working as a spooler at Brandon Mills. The couple was listed as "r10 Woodward," which indicates that they roomed at this location.
According to my mom, her parents first lived with Roy's sister and her husband, Tootsie and Doyle Clary. A quick look at the back of the book's address listing confirms that Doyle Clary was registered as the head of the household at 10 Woodward.
This information is for 1948 - a year when no national census took place. Without this directory, I would not know the couple's address for this time period. Based on library visits to view Atlanta city directories, I know that by 1950 Roy & Betty had settled in Atlanta at a Hotel owned by Roy's mother and step-father. Using Ancestry's collection, I see that the Clary's remained at 10 Woodward.
I hope that Ancestry.com continues to expand their city directory information so that other researchers will be able use these census substitutes. They really are a valuable resource.