The biggest change in the 7.x-2.x release of the Architecture module is integration with the Views module. Each architecture report is now a Drupal view and can therefore be modified using the Views UI. Exports to CSV are still possible by installing and enabling the Views Export Data module, automatically exposes an exportable version of each view. The default format is CSV and each download is available at the regular view path with "/export" added to the end (e.g. "/admin/reports/architecture/fields/export").
7.x-3.x is there for new development, and restructuring agreservations to make it more easy to implement
new and different workflow/booking modes (like hourly booking, daily booking, package booking, etc.),
by using at least some OOP methods.