I put TCAS to TA only when entering US airspace
Many airfields I visit have a note suggesting the use of TA only when doing parallel
instrument approaches.
I have to say I think carefully about this, especially when other a/c are on 'visuals' and there are people behind/to the side of me. Even though I hear "Oh yeah, we've got him in sight", it's not difficult to overcook a turn onto finals with the runway spacing at some airfields (SFO & EWR come to mind), not to mention the sheer number of runways to mis-identify (DFW are you listening?). This could mean a very late sighting (or none at all).
Sometimes I trade the likelyhood of an uneccessary go-around (or whatever) for protection from an unwanted whack up the a$$.
OK, so in 'TA only' you will still get a TA but if you can't see them and they are very close, the display ain't much help and manoevring might cause rather than avoid a collision.
I know ten years ago we didn't have any of this but having had my underwear (at the very least...) saved on two occasions by TCAS, I am becoming reluctant to let go of my safety blanket.