I’d set it up as follows:
- Mail for managing all email
- Calendar for all scheduled/time dependent items
- Reminders for all actionable lists: one list per next action context, agendas, waiting for, projects, and someday/maybe
- Notes for all reference items, meeting notes, project support materials, and checklists
- iCloud for document and photo storage
- Contacts for person/address storage
- Reliance on Spotlight to quickly find items and launch programs
This can be a quite effective system of strictly using Apple products, although I'd like to see greater integration between Mail and the other programs.