4 Stages Here
I'm in an enterprise environment as well, and we have DEV for development and unit testing, QA ifor functional and integration testing by our Quality Assurance team, User Acceptance Testng (UAT) for additional performance and integration testing against "almost production" data by our Quality Assurance team and by client representatives in many cases, and then finally production.
Other shops I've worked in have generally been 3 stages or less. I find the UAT stage here to actually be a welcome addition, as it identifies the problems where the clients didn't get the requirements right the first time and saves the pain of issues in production.
