I was in a similar boat, and switching to WP8 solved most of my calendar issues (and a lot of UI issues, as well). It also has very good support for multiple email accounts of different types. Not surprisingly, it has excellent Exchange support, but that's no guarantee it will be painless, due to the many bizarre configuration options offered to Exchange administrators:

1. There's no guarantee that autoconfiguration will work, especially if your address is user@example.edu but your server is exchange.example.edu.

2. You may be required to lock your screen with a password.

3. You may be required to allow remote wiping of your device (by your email provider, seriously?).

4. You may be required to enable ActiveSync in an out-of-band operation.

To make matters worse, error messages from any of the above tend to be completely meaningless.

But once you get past those hurdles, it's actually a pretty nice experience.

If you need to access calendars from other systems, you might be able to import or subscribe to them in your Microsoft account (live/outlook/onedrive/yahoo.com) online. I was able to integrate the school calendars of my children this way. It's not intuitive, but it's a set-and-forget task.