I love some Twitter's search operators. I looked up "Library :)" in Twitter, basic search, to get positive feedback, although I could have looked "library :(" to see what is bothering customers and get some ideas as to how we could improve our service. The same option is offered in advanced search, although the latter does make it easier to select your search specifications.
The variety of searches through third party search engines enhances Twitter's usefulness. I have always found #hashtag and Tweepsearch to be most useful. The question and answer services on Twitter can be very useful too. In fact Twitter can be a very effective tool when used correctly.