The 2 Twitter accounts I looked at were really quite different, which made sense since one was a personal account and one was from a media organisation.
This Way Up is a consumer programme on Radio NZ (which I sometimes catch a bit of after I've been listening to Kim Hill). The tweets seemed to be mainly informational, about what was coming up on the programme, or 'magazine' type items of interest around the topic of the radio show, most with links to other websites. The tweets themselves were in 'normal' language since they didn't need to be shortened to fit into the 140 character limit. So This Way Up's tweets weren't really answering the 'what are you doing' question, but giving information to people who listen to the show or are interested in the sort of topics it discusses.
I also looked at Margaret Atwood's Twitter account, which I found a rather different experience. The tweets were mostly in txt-speak which to be honest didn't mean a lot to me and I found difficult to decifer. (I am one of those miserable pedants who for the most part insists on typing text messages out in full, including correct punctuation where possible!) They appeared to be more social, conversational, sharing of thoughts and ideas and events rather than information, and very personal to Atwood and the people close to her. This did however seem more in keeping with the original aim of Twitter's creators, to answer the question, 'what are you doing?'
To be honest I can't really get excited about things like Twitter, which I'm sure have their place but do seem to have the potential to consume more and more time, though I like the concept of mobile access to a phone rather than logging in to a computer all the time. The blog post about the confusing Twitter terminology was also very interesting and helpful for someone using it for the first time.