I would recommend FTM. I bought my copy for $30 which I'm able to use on multiple computers. It not only provides backup for Ancestry.com but also a means of changing a batch of things all in one go - such as standardizing naming of a particular geographical location rather than living with the multiple versions you get from the various sources you attach. I still use Ancestry for input and most editing but FTM has lots of features that Ancestry lacks. It's also as far as I know the only backup scheme which captures your media as well as your facts/events.