Glider co-founder here. We hated how existing email clients treated an email from Paul Graham the same as newsletters and twitter notifications. Gmail's priority inbox tried to fix this problem by filtering out "unimportant" emails, but messages from different contexts were still being mixed together.
We think the best solution is to group emails by sender and context (people, notifications, mailing lists, etc). For example, if I'm a power-seller on eBay, my PayPal notifications are top priority, but I still don't want to see them alongside emails from friends. You already know what types of emails are important to you, so we designed Glider to allow you to easily see that information without having to create an intricate system of labels, filters and folders.
We'd love to hear your thoughts on email. We're looking for honest feedback, so please feel free to tear our idea apart. Is this something that you (or someone you know) would use? Thanks!