Office 365: Is 99.9% = reliable enough?

Per below, 99.9% up-time = 43.8 minutes / month being down.

For anyone who is presently using Office 365, is that 43.8 minutes typically in the form of planned Sunday maintenance, or sporadic down-time throughout the business day?

Thanks for any feedback or experiences.  We are seriously considering a migration from our on-premise exchange to Office 365 and want to hear from existing customers.

Thanks,
Mike

Here's the nines:

Availability %               Downtime/yr      Downtime/mo      Downtime/wk
90% ("one nine")      36.5 days      72 hours      16.8 hrs
95%      18.25 days      36 hours      8.4 hours
97%      10.96 days      21.6 hours      5.04 hours
98%      7.30 days      14.4 hours      3.36 hours
99% ("two nines")      3.65 days      7.20 hours      1.68 hrs
99.5%      1.83 days      3.60 hours      50.4 minutes
99.8%      17.52 hours      86.23 minutes      20.16 minutes
99.9% ("three nines")      8.76 hours      43.8 minutes      10.1 min
99.95%      4.38 hours      21.56 minutes      5.04 minutes
99.99% ("four nines")      52.56 minutes      4.32 minutes      1.01 min
99.999% ("five nines")      5.26 minutes      25.9 seconds      6.05 sec
99.9999% ("six nines")      31.5 seconds      2.59 seconds      0.605 sec
99.99999% ("seven nines")3.15 seconds      0.259 seconds      0.0605 sec
[MDT: 100%    Perfection     0             0                       0  ]