I feel like engaged Twitter users are a very selective bunch, with many of them being either Twitter marketers or people with A LOT of time on their hands and just like talking…neither of which are likely to be customers. It’s good for building short-term PR at best, IMO.
You’re better off dealing with Facebook or putting stuff on your blog, or even Youtube channel. Twitter is not good for business marketing but it could be good for business social networking. Go figure.