I'd caution over going too nuts about Outlook or Office apps and how they might affect/infect general Windows apps. One of the Office team's big "things" is to try and re-invent the look of the product every iteration. Yes, they did adopt the awful Office ribbon in Windows 8's Explorer, but the worst parts of it, like tiny buttons in the title bar and the counter-intuative File menu, aren't common in the rest of Windows or 3rd party apps.
I'd look more closely at apps like OneDrive, an actual shipping app not designed by the Office team. The latest WP OneDrive forces you to use a white theme even if it will drain your battery and has a hamburger menu (boo!), but for the most part it is designed like a standard WP app. It has a normal app bar with normal icon buttons and is based on a pivot control like many other 3rd party WP apps. The hamburger menu is only for account settings and enabling "shake for feedback". They will be rarely used, so it's not horrible in this case that the button is on the upper left. They apparently really didn't want the app menu to scroll.
I hate hamburger menus and love the Metro design language with equal passion, but I'm not ready to go totally nuts about it yet until I see software closer to release that isn't Office using the Office-like layout. That said, it's great that so many are putting the pressure on MS to stick with the Metro design language.