Nearly a week after Yahoo Buzz has launched, and I haven't found a compelling reason to do anything more than visit the homepage. I get the sense that this is the overwhelming sentiment and that Digg isn't losing any sleep over the much-hyped Yahoo property.
I have two primary complaints (and numerous others):
1) I am amazed that Buzz launched without allowing publishers (like myself) to post content. This is wrong on so many levels. First, readers don't want to read what is essentially a combined rss feed of Yahoo and USA Today. What makes Digg so enjoyable is it's ability to expose readers to varied and new content.
More importantly, it prevents Buzz's growth from a content and readership perspective. Digg has 'share this' icons / links on millions of blogs and there is a clear incentive for readers and writers to post their content to Digg (get traffic, build community rankings) - without that incentive, Digg would collapse, readers would have less content to browse, and the 'economy of content' collapses.
... And Yahoo has an opportunity to out-muscle Digg by delivering top content-providers more traffic than any other web property (and rumors are that Yahoo is willing to float top articles on Yahoo.com's front door).
2. Buzz has a few verticals: Sports, World, Video, etc. The verticals are nothing more than a sort order for articles. The top searches module on the right page is consistent on every Buzz page and Obama, Hilary Duff, and Iran (top 3 searches) have no relevance to the Sports category. There are power-users on Digg for each category and there are readers who only visit specific categories - there is no motivation to move beyond the first page on Yahoo Buzz.