Simply put, Gmail provides a compelling user experience:
* fast and accurate search. This is key, and I don't know of a single desktop email client that even comes close to providing a decent search feature. Decent here means "answer full-text queries accurately within a second or so". I didn't realize how useful this was until switching to Gmail; now I have it, I can't switch back. I don't even bother organizing my email more than a minimal amount any more, I just search for things when I need them.
* remote access is also key. I regularly access the internet from at least 4 different devices, on at least 3 different operating systems. Sometimes I do so while traveling. Gmail makes this convenient --- all I need is a web browser. IMAP need not apply --- I found IMAP appallingly slow last time I tried it.
My experience is the polar opposite. I have to rely on a native client to search because GMail search is so bad. It hasn't been that fast for a while -- waiting 30+s for a search is pretty routine nowadays. But worse, it's never really handled stemming well -- it has to be an exact word match, even for singular vs plural. And the number of false positives I get usually doesn't even make it worthwhile. I had resorted to deleting mail rather than archiving it, but that only helped marginally.
Having said that, I rely on too many marketplace apps now to make switching a reasonable alternative. So, I make do with native clients.
One account has 2.5 GB, another has 700 MB. I'm on a lot of mailing lists and get a lot of transactional email. I just timed switching a label and that took 4s on the smaller account. This is in Chrome with SPDY enabled, too, so I doubt it's client transport.
I should probably note that it tends to be variable with the time of day. That's not unexpected, but still kinda sucks.
Maybe it's number of messages vs size of store. Or perhaps because a large percentage are similar in structure (google groups, monit alerts, etc.), they cause indexing to perform poorly. Dunno. But I wish I had < 1s searches.
I use Rackspace Email, over IMAP on the desktop, IMAP on my phone, and webmail when on someone else's computer. It's never slow in any way. When I sign up for things, I hear the ding of the confirmation e-mail within 2-3 seconds of submitting the form -- fast as push mail.
You should probably check out who Harald Welte is and what he does before making such accusations. I don't agree with him here, but "link bait" this is not.
Simply put, Gmail provides a compelling user experience:
* fast and accurate search. This is key, and I don't know of a single desktop email client that even comes close to providing a decent search feature. Decent here means "answer full-text queries accurately within a second or so". I didn't realize how useful this was until switching to Gmail; now I have it, I can't switch back. I don't even bother organizing my email more than a minimal amount any more, I just search for things when I need them.
* remote access is also key. I regularly access the internet from at least 4 different devices, on at least 3 different operating systems. Sometimes I do so while traveling. Gmail makes this convenient --- all I need is a web browser. IMAP need not apply --- I found IMAP appallingly slow last time I tried it.