The challenge
Historically, the Signup module has been the go-to solution for managing event registrations (i.e., sign-ups) in Drupal. This venerable module has nearly 8000 reported installs, 14 contributors, and a vibrant ecosystem of additional contrib modules (such as Signup Integration for Ubercart). Signup is also a key component of the Conference Organizing Distribution.
All this considered, only 500 of Signup's installs are in Drupal 7, for which the module still does not have a tagged, stable release. And since the module must maintain an upgrade path for all those users, taking full advantage of Drupal 7's new features, such as the entity system, is very challenging.
Given ThinkShout's comittment to Drupal innovation, last year we began work on an entity-based alternative to Signup, drawing significant inspiration from the amazing work that was already done there. We were very excited about the benefits offered by an entity-based registration system, namely the ability to add custom fields of any type to a registration, along with hooking into the various entity APIs. We launched an early version of the tool on Manhattan Kayak Company's new website and started a conversation with the Signup team about possible collaboration. While productive and receptive, things were moving a bit slowly, so we started up a new Entity Registrations project on Drupal.org and have recently pushed the code to a point where we want to share and discuss it with the community.