As a general matter, any details we can discover about the lives of our ancestors helps bring them to life and expands our understanding of our history.  In fact for us, it's the most fun aspect of doing the research.  In other words, even if we know the basic information about a given line, there is still a lot more to be discovered.

We have been unable to positively identify any pre-immigration ancestors of William D. Johnson, Jr. for several lines although we have indications of places of origin outside the US:
     John Dickson--Glasgow(?), Scotland
     Letitia Richmond Eccles--Preston, England
     William Dawson--Canada

There are a number of matrilineal lines of which we know virtually nothing, several of which are recently discovered.  Often we will only have a first name for spouses and other times although we have a maiden name we know nothing of the wife's ancestry.  Examples are Hampton and Kennard.
We've always been curious about Charles P. Hawkins' move to NYC. As the oldest son, you would expect him to inherit the farm on his father's death.  But instead, at some point, he settled in NYC and was joined by two of his brothers. ...may never find an answer to that one but it is possible that the Hawkins brothers were encouraged to make the leap to NYC due to the presence of their mother's family there.
A visit to Dale Cemetery in Ossining, NY might yield information to help trace the Van Tine's (or as a starting point for research on Augusta VanTine's mother--at least getting her maiden name straight!)
Perhaps most critically for a "Johnson" genealogy, we have only managed to go back four generations from Wm. D Johnson, Jr. in the Johnson line and of Ephraim Elmer Johnson we know very little.  Although as of September 2001 we have identified Ephraim's parents as Nathaniel and Jane (Dare) Johnson.
What was the maiden name of Ephraim Elmer's wife Sarah?  She is listed as Sarah H. on her son Reuben's birth certificate and as Sarah B on the 1850 census.  Could it have been Henry, given son Reuben's middle name?  Were there Henrys in the area of New Jersey she came from?
Do the middle names of the children of Reuben Henry and Hannah (Dickson) Johnson give us any matrilineal leads?  (e.g., is Knox a family name and, if so, whose?)
William Dawson's life is another area where much more needs to be learned, and some of it should be relatively easy to come by since we know he lived with or near his daughter Grace in Painesville Ohio (his daughter Alice lived nearby in Glendale) and died there also.  Also, Letitia (Dawson) Johnson had an aunt who signs herself Alice E. MacGregor (we know she married Jack MacGregor) so could the "E" stand for Eccles and might she be Letitia Eccles' sister?