Email is secret elixir that makes us addicted to the Internet, but the overall infrastructure of it hasn't changed in over ten years. The same can be said for GMail.
The only way to deal with a high volume of email is to use filters, and GMail doesn't have that feature fully developed yet. There are no folders. You can "star" items and add colorful labels, but generally, it's just a stream of messages, with no emphasis on anything.
With GMail, I would let my inbox pile up to have hundreds and thousands of unread emails. I would quickly scan through messages, and click through if I had to, but I guarentee that I've missed some important messages. GMail does a good job of catching spam, but overall, it's sluggish. When I am on a long reply thread, after hitting send, a yellow box at the top says, "Still working..." and I'm stuck in an infinite loop.
I jumped over to Yahoo! Mail today to give it a spin. They are working on a new interface, but even their old interface has email filters with folders.
This is also the first time I haven't been afraid to delete an email.
Another simple feature that Yahoo! Mail has is a little box after you send a message, that asks you where you want to archive that email. They make an effort to help you keep your inbox manageable.
I also started using Yahoo! today because their address book and contacts list are easier to use. It's more integrated with the calendar than GMail too.
I will still check my GMail, but I'm definitely phasing it out.
Merlin Mann from 43 Folders published a Google Tech Talk called Inbox Zero last year, but I guess the GMail engineers didn't attend.
Let me know what you think of Yahoo! Mail. Are you a GMail user? If so, would you ever make the switch?