SaaS-based ZOHO Office, for example, keeps an audit trail of changes and offers easy interoperability and backup as well as federated logins with Google and Yahoo! Plus it's free.
If money isn't the issue, but power is, there's the long-running Corel WordPerfect X4, which boasts enticing document features and "fewer frustrating tics than the name brand." At $300 - $400, it's relatively spendy but still cheaper than Microsoft.
Based on Open Office, IBM's revived Lotus Symphony offers smooth, stable features and a combination of the international Open Document Format standard and MS Office formats. It's also accessible for visually disabled users. And it's free.