Status Update: Feb 18th, 2014
This module was originally created by fago as a quick solution for a problem, which solved it well while no other solution was available. At this point in time however, there are more robust solutions that are not only available but architecturally superior, actively supported, and under continued development.
We recommend those interested in subscription / membership sites to consider looking at commerce_license module as a solution. Out of the box it allows you to create "subscription" products that auto expire after a given time and can assign/remove roles from users. I would guess that this is the 90% use case of people looking at this module.
There is a single issue of "extending" a subscription if an additional one is purchased which is being solved/worked on here: https://drupal.org/node/2193305
I will endeavour to work with other module maintainers and get a comparison of commerce_sp, commerce_license, commerce_recurring, and commerce_subscriptions. I will also be seeing about creating a migration class / helper module for existing commerce_sp users to migrate to commerce_license and/or documenting how to create a simple membership site with commerce_license. If you have any questions please feel free to contact me.
- mrconnerton