I posted on the subject of Twitter a few months ago, when I was testing the waters of this technology, both for my comic and for my personal life. By now, I've figured out pretty much what I like and don't like about tweeting.
First of all, it's just not a big deal. I think it's pretty funny to see Twitter hyped on the news as the next cutting edge communications medium that all the hip and tech-savvy kids are into. Really, Twitter is a super simple technology, seemingly used by mostly businesses and older people, that allows you to broadcast your short message through a site that is all too often down.
I don't find it useful for my personal life; Facebook gives me a similar broadcast outlet with the benefit of allowing friends to comment on my posts. Additionally, on Facebook I don't have to scroll through reams of out-of-context conversations such as:
sometwitteruser: I knew it! RT @othertwitteruser It's all my fault! The apocalypse is here. (47 minutes ago from web)
Also I learned from day one that most of the people who followed me were basically shills for pornography sites, a common Twitter user experience I chronicled through Valdosta.
I do think it makes for a useful tool for promoting your product or service, since these types of posts aren't necessarily conversational and can be 140 characters or less without seeming artificially short. For this reason, while I've deactivated my personal account, I've retained @theremonstrance. So far I've mostly used it to announce new comic postings, but I do enjoy being able to follow other, more entertaining comic artists. I mostly see my Twitter feed through the iGoogle TwitterGadget; I rarely go to the actual Twitter site. When I had two Twitter accounts, I used the excellent and simple Matt web application to make posts.
In short, I would definitely recommend Twitter for anyone who wants to promote something (comic, band, dog walking business); but for personal stuff, I'd prefer almost anything else (e.g. Google Buzz) that allows for commenting, unlimited message size, and isn't always down.