This is huge for Twitter. As search becomes totally incorporated into the Twitter interface, the service will hit a critical inflection point. Search as its interface is the problem and the solution, and it’s great to see the progress being made (yes, finally). Twitter people search.
As for why I am so all over search as key to Twitter, I’ve got a much longer post in me about that, but at the end of the day, it’s way too hard to figure out how to make Twitter useful for “normal people” – IE those not in the ourosborosphere. Search will help solve that, and at the same time, create the inventory for TweetSense to emerge.