And there you go. If you're leaving Salesforce (or any system in favor of something new), you've already got a bit of a task ahead of you to get the data into your new system. Updating the file names would be a small part of your migration project. You don't want to delete inactive users. If you do, what happens to all of the activities they've logged, or opportunities they've closed? Each of those items contains an ID pointing back to the user object. If you remove the user row, you end up with a bunch of records that can't display a value for who created/modified them. To work around that problem, you mark the user as inactive (freeing up a license), then create a view of just the active users. Problem solved.

OK, I'll give you that one, but honestly, how often does an org need to export all of the attachments in their CRM system? Why would this be of benefit when you can simply log in to look at any of the attachments that are stored there?

I'm not sure what you mean here. You can export all of the data from any Salesforce object to csv. From there you can do whatever you want with the data. If you wanted a list of accounts and their contacts, you could create a simple report (or use one of the built in reports) and export to Excel or csv. What else do you need?

Salesforce donates 10 user licenses for free to nonprofits and then offers extremely discounted pricing on licenses beyond that. I work for a non profit that does technology consulting for other non profits. We implement Salesforce and have found it to be very flexible and extendable.