A while back I moved from http://grhughes.com to http://garethrhugh.es and I wanted to start using the same email address and retire the old one. I have been using Google Apps for a long time on the old domain and I tried to add a second email to my account with no success. I couldn't get it to send an email without saying via grhughes.com and there was no sensible way to change domains. I also had a few other issues with Google such as them dropping push support notifiation for iOS a while ago.
So I decided to give Office 365 a try. I've been using it for a few days and these are some of my initial observations.
The setup process was terrible. It makes you sign up for a year and pay before you get to try the service at all. I had issues with payment failing which made me refresh the payment page (always worrying) then domain setup failed too which I couldn't fix without detleting all the setup and restarting.
Then it took a day for the OneDrive apps to let me sign in on iOS without popping up an error. At this point I was really regretting my decision.
Outlook.com is great, much better than gmail now I think. The interface looks more modern and performs really well.
This is the weakest part of the whole thing, OneDrive is not as good as Google Drive. The web interface is okay but the mobile offerings are not good at all. There's 2 apps, it's not clear which to use, they both seem to support different functionality and neither of them are very good.
Office Online is really good so far, I have pretty light usage requirements but so far it seems better than the Google version.
2 factor auth is there which is nice, but it would be nice if you didn't need a different auth app for every service. I have at least 4 on my phone now. It's too much.