I'd say the 2001 material is probably revision 1 or 2. The current revision is 5. I have revision 4 and the biggest improvement here was that the 15th book of reference material was done away and split into the relevant sections of the first 14 books and sample questions were placed at the end of each chapter instead of at the end of each book. Both of these improvements would be a Godsend if using a PDF version and lo and behold, Oxford released their own CD holding the PDFs about a year ago. You'd think they had PDF navigation in mind when they moved this material into the chapters where you might need it.
It could be maddening to try navigating what I assume must be a scanned PDF version from a copyright infringement mill somewhere in the third world, but if it's just augmenting your FTO provided manuals, maybe it's worth the bother for occasional usage.