A more seamless switch would be using just the web clients.

Seamless but significantly more inefficient if you prefer the desktop app experience.

Unless you want to use firefox. O365 is unusable in firefox.

Why would you say something so bold, yet so false?

Maybe it's just me, but it is buggy to the point of being unusable every time I try it.

Example: When it is in the middle of popping up suggestions as you compose, it suddenly seems to decide you aren't in the compose window any more and interprets anything you type as a keyboard shortcut (e.g. "n" for new message "e" for archive). Since I type rather fast, this happens to me all the time.

There is such a thing as off-line. And, with email that can be a good thing for multiple reasons - except when trying to send or receive of course :)

With the current incarnation of Thunderbird there is even a switch you can flip to make the email client offline, even if your PC is not. Believe it or not, that is an extremely valued feature here.

I agree strongly with this. Even on workstation I have the default to Offline and decide when to let it poll the IMAP4 servers - great for not allowing distractions or interruptions except on your own schedule, not someone else's.

With synchronized folders and offline storage it makes composing, reading, and replying easy with outgoing queued until next time connected when out and about with a portable device.

That's the big point to me.

Realistically next time I buy a new laptop it won't be heavily premeditated: the odds are that my old one will die and I'll need something that works that week. I don't want to end up buying another Apple just because I don't have time to switch mail clients.

Obviously a mail client only takes a few hours to set up, but it's not just the mail clients: I try to avoid anything Apple-specific for the same reason.