I was ironically fired from the Apple Store I worked at when I overslept two hours because multiple alarms failed. Imagine the sinking feeling when I woke up and all the alarms went off, one after the other....the alarm contributed to other tardies, but unfortunately, there were other problems that contributed to poor attendance...I would have appreciated some grace though given the bug...
It has failed me many times, but I do still use it for everyday stuff. If it's something where I have to wake up abnormally early or something incredibly important, I'll set another alarm. I'm glad someone else posted this because I was beginning to think it was just me...the thing that seems to trigger it most is some kind of event happening on the phone, such as a text message, preventing the alarm from going off...that's been my only observation so far...