We haven't experienced any major issues with iOS 7 and iMessage in particular, though Apple has received enough complaints to issue a response. Apparently some users are trying to send iMessages but they simply won't go through, and Apple has responded noting that it's a bug and a fix is on the way.

"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," Apple told The Wall Street Journal. "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."

Users should be able to switch to SMS for getting their messages out, of course that defeats the purpose of iMessage overall, which lets you send free texts to other iOS users. It also wouldn't work on a device without a wireless contract, such as a Wi-Fi only iPad. Apple's next iOS 7 release, iOS 7.0.3, may include the fix that settles the bug once and for all.