>The gmail web interface has become really annoying of late. I don't think it's an impossible task to do better than them by any means.
Google exposes the mail through IMAP, no? why don't you use your own mail client with the google backend?
I've written support software for and modified open-source pop3 and IMAP software, and I've gotten partway through writing my own SMTP server, but I never even /considered/ writing a client interface for mail. If I'm providing mail service, I will provide you mail service, and give you smtp and IMAP (encrypted, of course) interfaces to that mail service. Heck, I might support an open-source imap to web interface, too, but the way I see it? running the mailserver and running the mail client are two very different things. If you primarily choose your mail provider based on the provided web interface, you are probably not going to be a good customer for me, because I consider the mail client to be outside of my domain as a SysAdmin. Also, I come from an era where web-gateways to IMAP were considered some kind of cruel joke.
I'm not saying that interfaces are unimportant, but it's a very different product than just managing mail servers. I'm good at managing mail servers. I have a difficult time coming up with someone who would be less qualified to write a custom web interface. (I mean, unless the current open-source imap-to-web interfaces are good enough; I can manage open-source software just fine; I'm just not a UI kind of person.)
Personally, I wouldn't expect the sorts of companies that are best at running mail servers to also be the best at writing mail clients. That, and I wouldn't want to give up control of my client to other people, because a lot of what makes up a user interface is personal preference. That, and there's no real advantage to having the same people run the server and the client; IMAP is well-standardized.