On the site "Software for Learning" Simon Evans talks about Twitter and its powers for enriching teacher knowledge through linking with a large pool of other educators and experts.
He has embeded an Edtalk from Chris Betcher who reminds us that to dabble is not enough to sell the tool; " Twitter only becomes useful when you have scale."
I agree...I joined Twitter several years ago and then left it as my lesast useful tool. I saw its power at Learning @ School in February, when I could discuss what I was hearing and seeing with others in the room; a great tool for someone like me who needs to reflect out loud!
I've also seen it as an effective way of publicising events, whether it be the latest word from a politician or getting people to look at the latest blog post (in many cases a good way of advertising your own wares!)
So get in there. It forces you to be succinct as you only have a limited number of characters to use.