updated 01:20 pm EST, Mon January 2, 2012
iOS 4.2.1 devices still affected
A problem with iOS alarms breaking on January 1st or the 2nd appears to been solved by Apple, at least in part, reports suggest. In 2011 the glitch caused some iOS devices to stay silent despite alarms being toggled on in the Clock app. Most iOS 5 devices have been working normally in 2012, according to posts at Engadget and TUAW, as well as some MacNN experience.
Still vulnerable though are devices running iOS 4.2.1. The gap is important mainly because v4.2.1 is last version of iOS supported by the iPhone 3G and the second-generation iPod touch. Those devices will likely never have fully-functional alarms, since Apple has never retroactively updated iOS, unlike OS X.