I've just had my first experience of using Turnitin and Feedback Studio for marking coursework essays. It didn't go well. I found multiple instances of students using too much text from their cited sources, having re-worded, edited or rearranged parts of them to various degrees. The Turnitin similarity scores were mostly pointless, as automatic matching was being made to other student submissions (which are inaccessible) rather than the original sources.  

A great feature would be to be able to exclude all previous student submitted material as matched sources and/or to check sources in the reference list as a priority.

Also, very useful would be to be able to use the hyperlinks in the student's document and/or copy and paste from it to a browser. As I couldn't do either of these I had to manually search for each source in the reference list to manually check for similarity. This took A REALLY LONG TIME!  I got very angry, frustrated and stressed having to find workarounds to work out what I thought Turnitin should have done automatically.

I tried all sorts of online help to find better answers, but there didn't seem to be any. I also have quite a long list of other characteristics of Turnitin and/or Feedback Studio that were annoying or unhelpful, if the developers are listening.