Google Buzz had a lot of import sources available at launch. There was so much noise from automated cross posting that I didn't even know that several of my friends were actively using the service until months later.
In contrast, Google+ is almost completely signal for me right now.
Yes, I was waiting for someone to bring up Buzz. I was also a first-day user of Buzz, and guess what? They allowed third-party import, and very quickly out-of-context Twitter updates overwhelmed my stream. Then there was a backlash, and the smarter people turned them off rather quickly. But the vast majority of people kept on using it. I think Google knows exactly what they are doing here.
In contrast, Google+ is almost completely signal for me right now.