I've always found the O365 admin centers very variable. I came to this thread because this morning they've been driving me up the wall (1 minute + page refresh times, intermittent errors moving between pages etc). But in the time it's taken to register my account to comment here it's suddenly come good. (Yes, I checked that my internet link wasn't being hammered while I was experiencing slowness at O365: the rest of the internet was just fine thank you very much - even the very latency-sensitive AJAXey parts of the internet).
Slowness in the O365 admin centers seems to be an ongoing problem though.
On a similar note, Microsoft's various federated sign ins have been historically awful (I must say that I was pleasantly surprised today when I logged in. It's been around four months since I last signed in anywhere at Microsoft and I'm seeing "new signin experience" banners everywhere. In the past I've torn my hair out on numerous occasions signing in with passport to log in to the microsoft partner center (I always cross my fingers when I see /adfs flash up in a URL moving between Microsoft sites).
Plus, there's too much sharepoint involved in Microsoft's systems. Anything that sharepoint powers is bound to be slow, clunky and generally hateful.
I almost never have these problems with similar sized systems at google or amazon.
Anyway, fingers crossed whatever Microsoft has done to their sign-in seems to have sorted out the old active directory federated services nightmare.
/end rant
