I am in a similar situation; however, not as bad as the OP describes. I teach full-time at a University that uses Microsoft as its backend. The school gives Office and OneDrive for Business to all its students. That is why I am interested in the SP3.
In addition, I teach as an online adjunct for another school, which uses Google as its backend. This is problematic. Here's what I have to do:
1)
Use the stock Windows app for Gmail. I have three different Gmail accounts and they all sync wonderfully. Yes, the features do not compare to Gmail in a browser, but at least I do not have to jump into the desktop just to answer students' questions.
2)
For calendaring, I use OneCalendar, which, again, keeps me in the Metro environment for scheduling. Again, the app is not as functional as Google in the browser, but it is quicker.
3)
Hangouts and Google Drive present an issue. I teach Public Speaking and all my students use Google Hangouts. There is no real solution in the Metro environment. I just use Chrome in the desktop. However, we only use Hangouts for speeches, which are scheduled for a certain time. We do not use Hangouts for unscheduled communication. If you use Hangouts in that manner, I can see the problem of always being in the desktop.
The same goes for my Composition classes. Students write in Google Drive so I use the Desktop and Chrome to collaborate with them.
The Chrome for Metro is very poor and useless for Google Apps. I found less headaches in using the Desktop.
(Full disclosure — I have been using a Dell Venue Pro 8, which I just sold, as I am purchasing a SP3. In addition, I was using a Nexus 7 as my Google device. Going from two to one device is what has me intrigued about the SP3; however, there are some major hurdles when trying to get Microsoft and Google to cooperate, especially in the Metro environment.)
Hope this assists. Cheers.