A lot of people feel that way about the pre-1850 censuses - since they don't name all of the people in the house, and since they don't give specific ages or other personal details about the members of the household, they are seen as having very little value. I disagree.
The 1840 census, for example, has this wonderful column in the middle of page two that lists the name and exact age of any Revolutionary War pensioner. These pensioners include the soldiers who served or their widows who received pensions after their husbands' death.
This column, taken from the 1840 Census of Edgecombe County, North Carolina, shows a neighborhood with a high percentage of surviving Revolutionary War vets. The youngest of these pensioners appears to be age 75 - not too surprising when you consider that this is the 1840 census and that the Revolution ended in 1783:
If you find a pensioner living in the household of one of your ancestors, you now have a brand new research tool - the pension file for the Revolutionary War pension that qualified him or her to be recorded in this column. These can be found at the National Archives, at Footnote.com, and at Heritage Quest. Your local State Archives may also have microfilmed copies.
Consider, too, that while it is possible that the pensioner is simply a boarder in the house, it is far more likely that he or she is related to someone in the household.
There is no such thing as a bad census - just some that are preferable to others.