I have found some vital clues to my CADY lineage via the IGI. I have
also found some errors. If you click on the link to the batch, film or
book number at the bottom of their screen, it will show you the
source. If the source is "Patron Submitted forms", I trust the entry
less than if it is, for instance, "Marriage Records for xxxx County
1853 - 1873". Even in the latter case it was still transcribed, and
typos creep in.
I have a book on another line of mine, LIVELY. It was written by a man
with a Ph.D. who lived in Salt Lake City. He took a year's sabbatical
to do it, financed by the National Association of Livelys. He cites
sources, notes discrepancies, rates his sources' reliability. It is
the most carefully researched genealogy book I've seen in 30 years of
looking at genealogy books. Even so, he has my grandfather's death
year as "1924" instead of "1942".
The moralof this is to check, check and check your sources.