Buzz has been met with mixed reception from users and tech pundits for various reasons. Some criticize it simply another social inbox to check, while others lament the privacy concerns, while still others feel it is Google trying to weasel into one more area of our communication. I understand all of these concerns, and they're all valid to a point. However, I am giving Buzz a fair chance and am actually starting to enjoy it.
Buzz provides a social connection right within Gmail. It allows you to see updates from your Gmail contacts using whatever method they've selected. Users can connect their other online accounts (Twitter, YouTube, Picasa, Flickr, etc) to Buzz so that whenever they update one of those sites, Buzz updates as well. You can read all Buzz's features here.
There's also a very strong mobile side to Buzz, and this is where I think it's power really shows. Google went to great lengths to create a very full featured mobile experience. Users can post updates, pictures etc. all from the mobile Buzz website, as well as post location tagged updates from the mobile version of Google Maps. There's even a Buzz layer in mobile maps that lets you see all the Buzz updates nearby. Read about all the mobile features here.
So what do I think? I think Buzz provides something unique. Yes, it has similar features to Facebook and Twitter, but it also trumps them in other ways. It beats Twitter by eliminating the character count, providing rich link and photo sharing and the very strong location based mobile updates. It beats Facebook by being open, promising to provide APIs, and being easily accessible directly within Gmail.
It's more than simple sidebar widgets that let you view Twitter or Flickr updates. It's a social sharing inbox and I think it has a definite place on the web. I've already seen the benefit of it. I have a few friends who are not Twitter users and therefore do not see my tweets. But they use Gmail and now Buzz, so they were able to see and comment on my Twitter posts without needing a Twitter account.
Another big plus for Buzz is that nobody needs to sign up for it. If you have Gmail, you have Buzz. The number of people using it is already very high and as such, I'm seeing a valuable update stream from my contacts already, only two days after launch.
Is Buzz perfect? No, there are definite shortcomings, like the potential privacy concerns (all of which can be allayed by simply selecting the privacy settings you want).
All in all, I like Buzz and I think it's going to get more and more useful down the road. If you're already a Gmail user, I encourage you to check it out.