It is entirely what you make of it, if you want to keep upto date with pretty much anything, people, companies, events then you can, it's entirely subscription based, so what you like you follow, you don't see anything else.
It isn't a social network in the same sense as the others, no matter how many times it's compared to facebook statuses. It's a micro-blogging service. You have your feed and you can add to it as and when you please, people can subscribe to your feed, and you can subscribe to a distinct set of peoples feeds.
You can get a lot out of twitter even if you never tweet. I'd say the biggest strength is collaborative communication, which is most common using hashtags, basically anything with a #tagname appended or within the message, makes it easier to search for, so if you're interested in #ge2010 (the general election 2010) you can just search that and see what people are saying at this point in time. Most twitter applications allow you to save a feed of a search so it will update like your feed of people you follow would.