I did try PowerPivot, which is nice and all, but a bit simple for what we were trying to achieve at the time. What year is it? It's the future, my friend - BOOM :-)
Wasn't my decision!
Wasn't just a report, it had user data entry as part of the system too and the users were very familiar with Excel, so made the exercise a lot easier (for them).
It's web-based, like intranet, where people within the organization store/share their documents. If you want to edit one of the documents/files, then you can "check it out" like a library and make your modifications, so that someone else isn't also trying to modify it at the same time. Then when you're done, you "check it in", again like a library.