I first read about Gmail's Priority Inbox feature some weeks ago, on Fred Wilson's blog A VC. Here are two posts about it by him: Inbox Zero and The Impact Of Priority Inbox.
At that time, I didn't try it out. But I enabled Priority Inbox today and checked it out (only a little, because it takes a while for it to learn or get trained to prioritize your emails well). My initial impression is that it is going to be useful, as Fred said. It may take some time to train it, but after that it should get better. Worth a check, IMO, if you suffer from email overload.
To me, the best thing about Priority Inbox is that after you enable it, a) you still have the option of disabling and re-enabling it through Gmail's Settings menu, and b) in the leftmost column in your Gmail, in addition to the Inbox link, there is now a Priority Inbox link, which makes switching between the normal Inbox view and the Priority Inbox view as simple as clicking one of those links. So you never need fear losing an important email that Priority Inbox thought was not important.
- Vasudev Ram - Dancing Bison Enterprises