Twitter started off being a tool for us when sitting in conferences – Barnaby Page from screens.tv questions the usefulness of that  BUT you have told us different and that you have found our tweets from events to be useful, interesting, informative and (importantly) fun. This has come from both those at the event and those not present and whilst that feedback continues so too will we.
Aside from conferences, we typically use Twitter on a day to day basis , as it was originally intended, for micro blogging – all of our breaking news goes out on Twitter first – including a lot of gossip and a hell of a lot of backchat!!! Think us strange (or anal) but we REALLY do like to get part of a story up on Twitter first before doing a fuller / more detailed ‘post’ on the DailyDOOH blog itself.
DigSignageToday, signagelive  and JohnRyanGlobal soon followed us in our use of Twitter and are all nice and active. Most recently ScalaInc  and Symon (in the guise of Steve_Gurley ) have joined the fray.
For those organisations that have more than one person tweeting then we have been playing with CoTweet. It might be worthwhile taking a look, see https://cotweet.com/ 
We believe that the jury is still out on Twitter and its usefulness but having said that we would encourage you to take a look at some of the industry tweets (above) and see if they are of any use to you.