There is no charge to use this. Advance registrations are not taken. You need to come to the library and sign up to use the computer. Each patron is limited to one hour if others are waiting. Currently, only the 1790 census is online.
Ancestry plans to add census years on a regular basis.
They plan to have uploaded 1790 through 1920 by January 2001. Some of these years will be searchable by name. This depends on whether or not an index has been created for that year. The 1790 is name searchable which is a great time saver. Of course, the indexing may contain errors so researchers may still need to do some page by page research.