I do not save an XML in the workfile - just PDF's of any iteration sent to a client. I keep zoning information - both a pic of the zoning map, as well as the zoning ordinance - when relevant (i.e. when there is zoning). Engagement letter, survey, any documents in the MLS repository (seller's disclosure, perk test results for drain field, whatever), site sales used for site analysis (along with the analysis), extraction documentation (if relevant), PC, farm list, and tax records for the subject and comps - to document prior transfers. Basically, anything I 'look at' that can be PDF'd is dropped into either the electronic or hard file. To Sputnam's point, my files are hybrids as well.