Security and control of access to system data and functionality is one of the main reasons people migrate from Quickbooks to a mid-range ERP system.
Dynamics GP provides basic security by allowing or restricting access to specific screens. These specific rights are combined into various roles which are typically assigned to each user as needed.
Dynamics GP also provides field level security that allows you to specify write, read, or hide access to individual fields within specific screens. It takes some additional work to set this up. But it can all be done from the GP user interface; no coding required.
This video shows how to simple hide a specific field from a specific user or group of users: http://youtu.be/ZzLH88fikz8