Please explain how EWS is broken, particularly as iPhone and Windows Mobile devices use the same interface.
EWS and Mail.app both use WebServices, iPhones, Windows Mobile, and Android devices use ActiveSync. Two completely different APIs. ActiveSync is intended for short bursts of data, sync'ng a few email messages at a time, it's not used for desktop applications.
Getting hung up on MAPI or not-MAPI is stupid. As long as you can get out of the thing what you need, who cares if it's MAPI or little mice running back and forth between between your computer and the server? And more specifically, you don't know what's involved in accomplishing what you're suggesting, particularly when it comes to porting to the multitude of platforms that access Exchange. It's all very easy to say they should be throwing all their resources at doing it when it's not you who needs to actually do it. So, once it's on the Mac, what about Android? iPhone? Everything else? Everyone will be crying poor. Never mind the fact that it's a closed box that was originally built years ago. Web Services is HTTP (natch). As long as they progress Web Services to feature parity, that's all that matters.
You're absolutely correct on people getting hung up on MAPI. MAPI is a dated protocol and is depreciated with each new release of Outlook for the PC (I believe all new calls use WebServices).
However, and it's unfortunate, but the reality is that MAPI is (currently) a more feature rich set of calls.
My biggest problem is that Outlook for Mac is essentially Entourage with a new skin. All the dialog boxes are from Entourage, as are all the old bugs that seem to have come along for the ride. Though I believe they've changed the error code of other users calendar items not syncing to -19999 though so that's different.
No side by side calendar viewing.
No server side rules.
No linking of .pst files (importing is not the same thing).
No archiving to .pst files (compatibility reasons, and what the hell is .olm).
No business card view for contacts (ok, that one is just me nitpicking).
Attachments are still encoded prior to uploading, which means when size restrictions are enabled, Mac users are limited to 75% of the true limit.
WebServices is a great improvement over WebDAV for sure, but this still isn't Outlook... and not because it doesn't use MAPI.