Earlier when twitter complaints started, it was very effective, now days it depends on how you tweet, its like escalation matrix in organization, you mark boss in CC better chance of successful response. i have had following success.
1. Getting overcharging shops in MAS reported/closed.
2. Getting coach attender to work
3. Getting on board cleaning staffs to work instead of taking a free...
more... ride.
3. Reporting incidents of unreserved people getting totally uncontrollable where there is a load of them, occupying reserved coaches at night and getting RP/RPF to act. etc.
positive tweets appreciating positive stuff, has been re tweeted many times by even RMs official id.
On the negative side,
1. Bringing to notice progress of project's
2. New trains
3. operational aspect etc.
have got standard canned responses, i still do it more or less like a reminder service.
Recently i have tried to raise issues in COMS application, as well