Research shows that still 59% of Twitter users are not receiving any response
Brands understand that social media can support their customer care programme if it's well-resourced and they have a clear strategy according to this Social Media Customer Service 101 infographic from West Interactive which focuses on Twitter customer service. It's working well for leading brands such as Nike and you may have seen Nationwide are promoting Twitter for customer support on their current TV campaign in the UK. Though how good are brands at providing a good user experience across their social media channels as '17% of consumers expect this media as a channel for responding to their customer service questions'.
Companies who are succeeding with social media as a channel for managing their customer service where they have a fully resourced social media team dedicated to answer social media questions across each channel and a Twitter handle purely for support. Having a clear purpose for your channel and good SLAs (Service Level Agreements for response) is an essential starting point.