Yes, I am on Twitter. In fact, I have two accounts. One is for FEAT-related content (@AdventureFEAT) and the other is mine, which I use for adventure racing/running/event content (@AdventureLisa).
I'm not very good at using either and although I post tweets here and there, I don't 'follow' anything or anyone on Twitter with any regularity. Actually, with none at all.
It's probably because I administer a bunch of websites, Facebook pages and email group lists that Twitter is, for me, the straw that breaks this social-media camel's back.
A few years ago I followed the Red Bull X-Alps event online with live tracking, and with Twitter. There were not that many people on Twitter and the content was very constructive - like notifications by followers of the weather conditions, when competitors were taking to the air. This meant that I didn't have to keep an eye on tracking all the time and if something what happening, we found out about it immediately on Twitter. But now, with thousands more people on Twitter now, there's just too much traffic and nonsense to make Twitter of any use (I'll stick with online tracking).
And I enjoy using and following Twitter for Expedition Africa, where all tweets relevant to this expedition adventure race are hashtagged #expafrica.
For me, Twitter is that much of too much although I do appreciate that it is the social medium of choice for many.