I just discovered a little while ago that Ancestry.com has just released their index for the 1940 census for Michigan. I immediately began searching for my people. I found some of them, but a few still elude me, like my grandma's sister and her killer. I admit that Salpatrick is not a common name and is therefore prone to transcription errors, but no matter how I search I can't find him yet. While searching for Joseph Salpatrick I looked at another record on which the wife's name was transcribed as "Simmons" when it very clearly said "Suzanne." I know I try to be careful in my indexing so I can only hope I will have better luck when the next Michigan index makes its debut.
FamilySearch's indexing of Michigan currently stands at 55% so it looks like I'll need to wait a little longer. Just an interesting note about Michigan's 1940 population, it seems to me that a LOT of Michigan's population lived in the Detroit area. Indexing has progressed alphabetically by county and I have been working on Washtenaw county lately. It looks like I'll spend the rest of the indexing period deciphering names in Wayne county.
To begin searching Ancestry's 1940 census records for free (through the end of 2013) click here.
As of September 2012, the 1940 census index for all states is also available at Family Search. Randy Seaver of GeneaMusings did a few comparisons of the indexes at Ancestry.com vs. FamilySearch and found that in general, the FamilySearch index seemed to be better. That is to say that his interpretation of the names he compared (and I concur) was in agreement with that transcribed by the FamilySearch indexers more often than the Ancestry indexers. Whether the transcribed names are accurate, spelled the way those who were enumerated spell them, is anyone's guess, however.
The bottom line is that if you have been using the Ancestry index and have not found some of your people you should try the FamilySearch index and see if you have better luck there. Maybe you'll get lucky!