Footnote.com has now entered into the same business, offering census images at much lower prices. The company presently provides the 1860 and 1930 census records online and has announced that the remaining images will be added in the next few months.
FamilySearch.org is also offering some census records online today and is planning to add many more. Of course, FamilySearch.org offers these at the lowest price possible: free.
Beau is a former Ancestry.com employee who later became Vice President of Content at Footnote.com. He has since left that company also but he now has an insider's view that few others possess. In his blog article, Beau provides a comparison of the services and offers his own comments as well.
You can read Beau Sharbrough's interesting article at http://tufblog.com/2009/12/05/footnote-census-and-familysearch.