Question? on FTD's

Hello everyone, I currently have a college project that deals with some of the Pros and cons of FTD usage,Flight Training Devices, and I wanted to get some input from those of you who are real world flyers such as me. or that attend any university majoring in any aviation related degrees. I just basically want to know why or why not should FTD usage should be increased or decreased, maybe even in relation with the type of rating you are currently working towards...hope to hear from youThanks a TON!