I've quit academia after about 10 years and Twitter has been invaluable to me, not just as a source for new research but also a source of contacts, collaborators, and 'different ways to do things'. But I always felt like we researchers on Twitter (and like OP) were all kidding ourselves: it's an echo chamber where the hyper-online researchers mostly talk to each other, 'public outreach' part is more a random chance occurrence, a byproduct.