Personally I have found no use for Twitter in either my professional or personal life. I have tried it, but I just didn't fit the way I work. In comparison to the blogs in my feed reader, Twitter:
1) Overwhelms with the amount of useless information, amongst which there may be something relevant.
2) Does not encourage the depth of reflection and thought that I value from blog posts.
3) Becomes a conversation between people, but you can only see one side of it.
I realise that other people value the immediacy and connectedness that Twitter brings, but does that come at a cost?
I've heard so many people talk about 'the four stages of Twitter', without really being able to back up what they are or why I should put in the effort to go through them to achieve Tweet Zen.
Twitter IS useful to me - though it's taken a lot of effort to find the right group of people to follow. I recently pruned all the Stephen Frys, Guy Kawasakis etc out of my list - because people who answer the question Twitter asks ('What are you doing?') are using the tool for what it was designed, but not for what it is being used.
Having the right group of people on my twitroll provides me with a rich and varied source of material, links, articles and occasionally light relief. In that sense, I find it hugely helpful for personal learning - in an exploratory, self-paced way. I post snippets about learning and so on, but only in duplication with other channels - because research has shown that twitter is very much a 30- and 40-something phenomenon, so I'd be missing the grads and the grey-hairs if I relied on it exlusively.
I think twitter is great for building and communicating with a network of people with similar interests. If all your network are using it to share their experiences, then it can be a great tool. I use twitter as 'microblogging' but increasingly as a replacement to my RSS feeds. Bloggers I follow tweet updates, so I can now stop being stressed out by that ever increasing number in my RSS reader!!
I think Twitter is a very useful tool, if you find the right people to follow u can find the news and info that you are interested instantly after they are published in the internet because most of the people you follow are also interested in the same topics so as soon as one read an interesting article or news on the internet they Tweet it and you can easily get informed about it by reading less than 140 characters and not a full page.
This amazing tool can be used a lot in learning as it can distribute essential and important pieces of knowledge among people who are gaining knowledge in the same field.
Twitter is a fantastic tool - but it's a tool and that is the important thing to remember. It's just one of the ways in which I can find out information and interact with others. I feel that it's not dissimilar to talking about email. I'm sure you'd agree that email is a useful tool but sometimes we have to remind ourselves that we might be better off giving that person a ring rather than sending them an email!
The problem with these popular things is that people see them as a panacea for all their ills or as 'the only tool'. What is great about Web 2.0 (or are we on 3.0 now?) is the sheer range of tools available to us for learning.
Twitter is being used in a few universities now and even in primary school classrooms (here's a video on Teacher's TV showing a Spanish teacher asking people on Twitter what their favourite animal is and getting replies in real time, in Spanish, for the class: http://www.teachers.tv/video/37336).
It's also superb for developing your own professional network. I can ask people I know on Twitter a development related question and get lots of different views and suggestions - the world is your mentor!
If you find it difficult to separate the wheat from the chaff on Twitter, I recommend Tweetdeck which enables you to have separate columns on different themes - so I have a 'news', 'comedy', 'e-learning' etc. column - this is much easier to manage.
The main thing to remember is that Twitter is a tool among other tools and not the be all and end all!