As much as it hurt me to upgrade my Nav/Comms to FM Immune at the end of the day if there was not a risk then there would not be a requirement to have it done.
The last thing I wanted to find on an approach in bad weather was that the indications were incorrect becuase of FM interference.
At the end of the day IFR flying requires appropriate equipment and appropriate skills/practice, FM immune is just part of it.
It cost me US$600 to have 2 x Narco Nav/Comms made FM immune hardly a huger amount of money for safety?