I had this bug since Beta but really didn't think much of it. When I have a timer going, the lock screen just shows 00:00 on my iPhone 5. I did upgrade to the final GM, though it wasn't directly through iTunes. I noticed last night my iPad 4 does not have this error, which I updated OTA from 6.1.3 to 7.0 the day 7 came out. A co-worker has a 5 and his timer also shows fine on the lock screen. Guess it's just me. Anyone else have the issue? May try a complete wipe and install tonight.