I am not a fan of Twitter chats. These seem an example of the “I only have a hammer” mentality.
Twitter facilitates. It is the means to various ends. It may motivate the engagement some need to pursue certain ends. It may help you identify (discover) resources related to ends you want to achieve. However, if all you do is follow Twitter and maybe even tweet now and then, I would argue you are missing out on most learning opportunities.
The 140 character limit is the culprit here. Within this limit, you can be directed to meaningful content, but not experience meaningful content directly. You can direct others to content that you have learned from composing. However, the composition must occur elsewhere.
The 140 character limit combined with the time to post and read posts limits the efficiency of group conversations. I say this in reaction to what I have observed in group chat conversations. Limited time to think, limited time to produce, and a limit on what can be stated are a combination resulting in little accomplished. I think people like the experience of interacting in real time. They fail to take stock of what really gets done.
I think a tool not limiting input would address some of these challenges. So, for example, google hangouts allows both interactive audio and text chat. As long as participants come prepared my experience has been the conversations are richer.
It is my perception that preparation is an issue in most chats. Once lack of preparation becomes the norm, both the number of responses, the depth of responses, and even the questions posed change. If this is to be the situation, an old-fashioned discussion board makes more sense. There is no pressure to “shoot from the hip” and there is the opportunity to use earlier responses to generate ideas in new responses. An hour spent with this format while typically not synchronous would typically be more productive.