Used it to capture respondent data for a unique research tool we run. Got good results. Had to custom-code all the server/client interactions to handle MTurks' requirements. Went well. Still use the content from MTurk users as demo of "...how to get unique insights from your consumers". As things progressed, stopped using it. However all our project setup/server/client code still have variables/functions that start with mturk_. Not causing any issues, so there they sit. I feel guitly every time I think about not having cleansed the code. BTW: Just added new custom code for Prolific. Hoping to test their respondents this week. However Prolific's affect on the code was nothing compared to interacting with MTurk's servers.