The right FTD may be useful for some specific non-instrument work as well.
In my view a full-size unit that reasonably emulates the machine a student will be using is useful for initial familiarisation and mnemonic work.
I have also witnessed significant improvements in students who have used a FTD to deal with certain aspects of flying that they were having issues with - for example crosswind landing. The ability to pause, rerun etc just on the base leg has proven to be invaluable for some...