RA
The time for the actual RA to be displayed to the controller has to be relatively small for the function to be able to give any benefit except for statistical use.
In general my impression (theoretical - not hands on) of the mode S downlink reaction time is that it is to slow to be of any direct use. Lets say RA protection give 30 sec prewarning, with 20 sec assumed time before display to controller this leaves about 10 sec for contoller to notice and think of his options and act (reads basically - nonoptions/not act)
This is simply not anywhere near what is needed to be able to sort out a situation - it can take 30 sec to get a word in on a busy freq even for the controller (bad case ok but anyway). Then consider that the controllers controlling-role is more or less over the second the RA comes into play.
I remain to be convinced of the use of this except as for statistical and investigation info.