GSD used Rollup Helper internally to help them keep track of logged time, invoices, payments, expenses, and projects in custom objects. This included some with lookup relationships where data needed to be rolled up across objects. Because time entries are not master-detail to Invoices or Payments, they needed to rollup time across those two objects in real-time.
The team at Passage Technology used Custom development rollups using Apex. First they used Rollup Helper to rollup time and dollars. Next they pulled bill rates from certain objects to multiply them by time, and rolled up the time and amounts from Time Entries onto Invoice and Payment objects. They then issued Invoices and Payments using DrawLoop DDPs.
Passage Technology's solution gave GSD the flexibility they needed as they built out their functionality, which provided immense value. Rollup Helper saved them valuable time involved with developing their internal project management and billing solution. Without it, they would've needed a developer to change things multiple times as they nailed down their data model.