Looks nice. I am in finance and have developed reporting/querying tools for accounting teams. The most important thing is catering to Excel. That's just the way it is. What I mention below might already exist and if it does that's great, you're on the right track.
1. The ability to input a list of cost centers/accounts and export all journal entries to Excel is a requirement
2. An Excel add-in is a better selling point than the built-in spreadsheet feature.