Well, against all odds, Google Buzz is starting to gain some momentum. Things started off rocky when people were concerned about privacy issues surrounding the Buzz launch. But now, they are pushing through the problems that plagued them at first, and have started to become "cool".
The Buzz API was the first step to winning over the hearts of developers -- the second step was cracking it completely open and offering a free Firehose API. Now people can really start making interesting buzz apps.
Twitter was the first to offer such an api. Their real-time api's are pretty wicked, but good luck trying to get access to their Firehose unless you've got lots of money. Granted, there are very few use cases that can't be developed for using other public Twitter API's.
As Google opens up Buzz to developers, I'm guessing popularity of the service will increase. If you can be that API people use to learn how to consume API's, you've got a good shot. Google used to be that with the Google Search API -- then, after they pulled the plug on that, Twitter took their place as the "hello world" of choice.
What do you think?