If Microsoft-only is not acceptable, why is Google-only acceptable?
Sure, you can access Gmail from virtually any computer. But then, you can access Windows from virtually any computer too (just run it in a virtual machine).
They're both proprietary. The only difference I see is the price of Gmail is $0 and the price of Windows is approx $100. But, frankly, if it's just about price you might as well buy a phone which is $100 cheaper.
If I had an Android phone, I'd like to use the calendar and email sync features, but I'd rather do it to another provider of my own choice, probably one which does a few things differently to Google.
Seems Android's software only works properly with Gmail though, and might stay that way.