My team came across a solution which allows to:

- convert XLS+DOC+PPT to PDF
- replace strings in DOC files
- read/write Excel files using simplified aAPI like getCell and setCell
- hide sheets in Excel files(hide secondary calculations for example)

Available on this website: dancrintea.ro/xls-to-pdf/

The only downside is that it needs OpenOffice,
but hey..... a lot of nice things things are possible this way.
Can you please share your tools and experience on processing MS Office documents with Java?