For a long while you could go to:
to run a speed test from the Microsoft Online datacentres to your location. Doing so would produce some handy results like:
if you try and visit the site above it comes up as not found and I haven’t found any replacement as yet?? Strange.
For the time being I suggest that the best substitute is:
and select the Office 365 tab
as the best way to get an idea of the performance from the Office 365 data centres, although I’d prefer to see the old site back as it provides a lot more ‘techie’ info. I hope it is getting revamped in preparation for the upcoming release of the new Office 365.