Mixed feelings, really. I found it necessary when I had the big silly windows mobile brick (MDA), less so now that I have C's old phone, which actually works as a phone.
It was nice to have that answering ability right there on my face, and to have my hands free to do other stuff. On the other hand, it was tricky getting one to be comfortable, and as is true with me and small electronic things, I've treated the two that I've had pretty roughly. I accidentally tossed the first one into the brush by the river. The second one (a Jawbone previously belonging to C) has been dropped out of a pocket, stepped on, and run through the wash. (Really.) It still runs, shockingly enough, although it took a while to take a charge the first time after the laundry incident.
If I get a new smartphone, I'll probably either go back to using the Jawbone or pick up another headset, but as long as I have ye olde flip phone I'm in no hurry. 🙂