Well, if used with intention and wisdom for long rides, I think it's ok. I wouldn't call them "arm rests"

Yes, it's not just "rest", and you have to train for them as the handling is different and your body position changes the muscles that are used, and never ever use it in a paceline. But using them also makes you last longer and you can beat the wind.

I know some of our longdistance riders here have them.

True, if your bike does not fit you, especially if you're too stretched out, aero bars will not make you much happier.