Evaluate use of Excel exports throughout Moodle

After some problems with creating database activity module exports (see MDLQA-964 and MDL-19864 for details), it appears that there are various places where we have Excel related code. It would probably be a good idea to go in and remove any duplication and settle on a single approach that seems reasonably reliable. Here is what I found so far:

lib/pear/Spreadsheet/Excel
lib/excellib.class.php
lib/excel/*

Some questions that came up in discussions:
1) Are the libraries current (updated)
2) Are there other libraries now that produce more recent versions of Excel (Biff8 is essentially Excel 5 - prior to 2007, etc.)
3) are we using one single library/approach to creating the Excel files?
4) should we continue to support xls format

I wonder if there is a way to create the Open Office Calc file (or a CSV) and then simply have that converted to an xls file.

There may be other issues as well but I figured this would be a good place to start a conversation. I'm attaching a grep of the code base for any file containing the word excel.

Peace - Anthony