Muscle memory is a bitch. Especially when making the switch from desktop apps to web apps.
I've been alt-tabbing between applications for 15 years (1992 marked the introduction of Windows 3.1, the Version That Mattered). I've only been CTRL-tabbing between browser tabs for what, three years? The mental model of "to switch applications, alt-tab" is deeply, deeply ingrained; ctrl-tabbing between gmail, gcal, gtalk and gdocs just isn't the same. My recent preference for web applications is bumping up against a decade and a half of
repetitive motion learned behavior.
And look, here's the comment bait: I know I can't be the only late-30something who's having issues adjusting to our brave new world. What's blocking you from going all web all the time?