Sally - I used them once in a very long while, but that was before my cell phone went digital. Honestly, I think the last time I used one was back in 1999 on a 767.

The A321s have a spot for the airphones, but every single one of them I've flown do not have the phones installed (so I've managed not to fly on the ones that do have 'em. YMMV). The 319s and 320s have them on some of the aircraft, but not on all of the others. The Boeings have 'em on all of the aircraft, IIRC.