Whoa whoa, hold it right there. Unless your webmail supports simple keyboard shortcuts (like 'A' for archiving), threaded messages views, multiple email accounts at once and few other useful-but-not-for-majority features, snark statements like that are unfounded.
Right before we were acquired, my company had just upgraded to the latest Exchange suite, including Live messaging, Round table in all our meeting rooms, and VOIP phones. I am not a fan of MS generally, but everything worked pretty well together. Going from that synergy to a Zimbra/Thunderbird/Cisco Phone/Jabber chat where nothing was integrated with each other was pretty jarring.
It also doesn't help that my current company uses google for mail, which I think is pretty good generally and of course search is great.