I never trust wakeup calls or the clock radio in the room. In fact, I unplug both as soon as I get there. (I can tell you nightmare stories of the damn clock radio going off all night long from the previous guy who had an early-morning departure.)
So, instead, I set up my own alarm(s) on my laptop using a very simple shareware program called iAlarm:
http://www.xultrasoft.com/iAlarm/
It's a GREAT piece of software because it lets you choose to hear a beeping, a spoken alarm, a weather report, a podcast, any iTunes playlist, and more!
Worth every penny! Very reliable.
(I have no connection to the software company other than being a satisfied customer.)