Update 2: Apple is reporting that the iCloud.com services have also been restored.
Update: Apple is reporting that the availability of some services has now been restored but several features of iCloud are still down and undergoing maintenance.
As noted by Apple’s system status page, a multitude of Apple services are currently experiencing instability and downtime for some users. The affected services include the App Store, Mac App Store, Apple TV services, iTunes In The Cloud and critical features like Find My iPhone. We have also had a few reports of Apple Music downtime, seemingly repeating the outage yesterday, but Apple’s official status report does not mention any problems with Apple Music at this time.
Earlier in the day, Apple also says that some users may have been unable to send or receive iCloud mail or access cloud Notes features. An ETA for resolution of the problems impacting the majority of Apple services has not been given. This is obviously an exceptional situation, it’s hard to remember the last time this many Apple services were down simultaneously. We’ll update the post if we hear any further developments.