Why Buzz does not pull in tweets in real time is extremely curious, given Google's much-publicized relationship with Twitter, their focus of late on recency in search, and of course, Buzz's centering around standards, such as PubSubHubbub, a big player in the real-time world. That Twitter does not support PubSubHubbub is obviously one contributor, but other services have managed to find a way to get Twitter updates with practically zero delay, through leveraging Twitter's APIs. The result is a truly unsatisfactory experience, contributing to many people removing Twitter as a service feeding Buzz.
The way Buzz polls Twitter for updates now can mean older updates get pulled in as new along with more recent items. To date all "new" updates were added concurrently, but now they will be redistributed using the timestamp of the tweet from Twitter, in effect shuffling those updates throughout the network. This will make Buzz's mysterious "unread" counts even less relevant, and should be seen as a band-aid.
Updates from Twitter Now Shuffle In By Their Official Timestamp
Josh Wills, an engineer on the Buzz team, explained:
"Personally, I really like Twitter, and I want better integration between Twitter and Buzz. My hope is that this is a temporary change until we work out a way to play nicely together that is beneficial to everyone."Josh went on to say that the changes were intended to "make things less awful" while things get "worked out" to make the tweets appear in real-time. Whether that's a business development decision or an engineering one, to make things "play nicely together" was not explained, but he added that he believed "real-time twitter updates don't make sense w/o the highly-anticipated source filtering."
The ability to hide sources, such as Twitter, from one's feed in Buzz will be as important as it has become to hide services in FriendFeed, or to stop seeing Farmville updates in Facebook, should you not be interested. While Buzz has been fairly close-lipped in terms of talking about future features, Josh's comment referring to the filtering shows it's on their radar, and no doubt coming, rather than being speculated about endlessly by hopeful users.
Older Tweets that do enter Buzz can of course be made more prominent if they gain conversation, and therefore, get bumped to the top of your feed - but from what I've seen, most engagement comes on native items on the network.