In a statement, the company said:
We are aware of an issue that affects a fraction of a percent of our iMessage users, and we will have a fix available in an upcoming software update. In the meantime, we encourage any users having problems to reference our troubleshooting documents or contact AppleCare to help resolve their issue. We apologize for any inconvenience this causes impacted users.Affected users -- including some we know personally -- have seen their iMessages appear to go through, only to later appear with a red exclamation point, indicating the message did not go through.
Users have resorted to sending iMessages as regular text messages, rebooting the phone -- which reportedly, fixes the problem, but only temporarily -- and resetting the Network settings after disabling iMessage, then turning iMessage back on (To reset the Network settings, go to Settings - General - Reset - Reset Network Settings).
Complaints of this nature are not atypical for a new iOS release, and usually die down after a time. Other complaints include poor battery life, missed characters while typing, and poor Siri response.
Last week's 7.0.2 release addressed a security issue. When the iPhone 5c and 5s released, they did so with an immediate OTA update to 7.0.1 once the phone was activated, to fix 5c and 5s specific bugs.