It's really down to who you follow, and segmenting your following using the 'lists' option. I have lists for news, music, technology, friends, breaking news, and see at a glance what's going on. Using a third party application like Tweetdeck makes monitoring Twitter and your lists a doddle. I use Tweetdeck's Chrome application, which runs in a tab -
http://www.tweetdeck.com/chrome/.
Hashtags are great way of finding and interacting people discussing a particular topic. Following #bbcqt for example is great to see live reaction to Question Time, and to interact directly with others on the same topic. Speed is great, 140 characters instantly available, so news breaks fast and often first on Twitter. (An element of caution is therefore required).
Whether you can be arsed to contribute or not, by separating the wheat from the chaff and following the right people, Twitter becomes a great resource of knowledge, news and information gathering.