The status site says that only 1.1 percent of iCloud users are affected, but you wouldn't know it by the volume of agitation on our tip line. Since yesterday morning, iCloud mail connectivity has been iffy or entirely absent for some subscribers, and Apple's not commenting aside from the "we're working on it" notice.
It's unfortunate timing, given that Apple would prefer everyone focus on the shiny new hotness today. It's also a reminder that the cloud is hard, and providing reliable email service for 99% of your customers doesn't really meet the standard.
If your iCloud email is munged, let us know where you are and how long you've been out. The support discussions seem to be weighted a bit toward non-US users having issues.