This is a great plugin: I've been using it on an intranet page for the people whom I teach in a long-distance training course, as it's a good way to share information in real-time without having to send out a whole bunch of emails.
One suggestion though: it'd be great if there were more custom options on the Twitter side of things.
For example, I would love to be able to overwrite the automatic tweet and put in a more informative sentence. Having the first 140 characters of a live blog post is often very meaningless, unfortunately, and there's no way to click through directly to the live blog page either so that a student can quickly see what it was all about.
I'm not well-versed in the nitty gritty of working with WordPress, but perhaps we should be able to type a custom tweet in a textbox, and the plugin could test whether the post author has typed in a value. If there is a value, the plugin could send that as the tweet instead of the automatic 140-character string.