You think so? We've talked to a few law firms, and it seems it's a really hard market to crack. Docx support was our next feature before we decided to halt new feature development.
Maybe sell it as a plugin for MS Word? Querystorm[1] (ThingieQuery, previously), a plugin that allows SQL queries on Excel spreadsheets, seems to be doing pretty well.
[1]: http://www.querystorm.com/