I'm not sure. My phone is almost always on at work as an ebook reader, or I"m surfing the web on it. It lasted about 8 hrs of continual use before I installed the app, and about the same after.
I did run into a lot of Force Close issues, due to it conflicting with the power management settings. So I uninstalled it, and set my power management to Performance Mode, instead of On Demand.
Same results, with the alarm clock. Seems to be working in Preformance mode, but not in On Demand.
Makes me kinda think if you raised the Min CPU setting up a few notches it, the alarms might just work fine in On Demand mode too. Haven't had much time to play with it today though. Had to watch me some UFC! lol. I'll test it, and play with the power management over the next few days and get back.