Hello!
Instructors don't like "ex FS" students because they allegedly spend the whole time looking at the instruments.
Depends, I would say. I do mostly instrument instruction, and from what I see, the girls and guys who practise at home on their PCs or Macintoshes (using X plane) perform better than those who spend their evenings in the pub.
It's important however not to fool around with the sim (like trying to land a Concorde on the aircraft carrier) but to spend the time actually working. Doing R/T, reading checklists, following procedures and practising the difficult stuff like NDB interceptions and holdings.
Greetings, Max