I think that email clients are important, and worth a little criticism. We all use email, and lots of us complain about it - especially professionals. It's such a critical tool for our jobs, and it's frustrating when it doesn't work as well as we'd like, or when it distracts too much when we have better things to do.
What's my philosophy on email? If you want the original inspiration in long form, check out what Merlin Mann has been saying for years now, at Inbox Zero. The short version, which might look funny on a site where I plan to talk about email clients, is that most of what people don't like about email isn't the email software's fault. If email is a huge problem for your work, you probably can't solve it with a better client. I can't agree more.
However, that's no reason not to insist on continued improvements in the one tool every single knowledge worker uses, and that's what this site is about.