Auto back up is me hitting save frequently. One of the people working with me turned on the auto-save and it slowed the computer down way too much. He turned it off.
Auto-save is always a pain when you're dealing with the 100+ megabyte files common in publishing. The only thing that can solve that is a fast, multi-processor computer and a really fast hard drive. Or even better, an XServe RAID attached with fiber. 400 MB/sec write speeds shouldn't slow you down much even for huge files.