I love gmail priority inbox. I can't imagine doing email in an email client that doesn't have this feature. For those who are not familiar with priority inbox, it's a feature that splits the gmail inbox into three sections.
The top section is your "priority inbox." Google tries to figure who are the most important mail senders to you and it puts their mail in the top section. You can and should train it by using the +/- buttons to identify who is actually priority and who is not.
The middle section is the emails you have starred to return to later.
The bottom section is "everything else." For me this is mostly mail I don't want or need but it not technically spam. I do a quick scan of my "everything else" mail every day or two and pull the one or two emails out of it that I want and then delete the rest.
Now that we've gotten through what priority inbox is and why it works so well for me, I'd like to suggest a new feature to the gmail team. I'd like a "super priority inbox" which would be a fourth section on the page and above everything else. I'd enter the email addresses of a couple dozen people who I always want in my super priority inbox.
I know you can do this with filters and labels. I've done it. But the layout of the main inbox page in gmail is powerful. If I have to click over to a label to get to a filtered view, I just don't do it regularly.
One last thing about priority inbox and super priority inbox – it is even more awesome on mobile. The gmail client for android supports the priority inbox and ideally would support the super priority inbox when this feature is rolled out
