I have a good deal of insight into this, as I'm one of those fire alarm guys. I've been to buildings where the management was specifically notified weeks in advance that we'd be there on a certain day to test the fire alarm system. Unbeknownst to us, they didn't bother to notify anyone. Some people ran for it when the alarm went off, others didn't even notice.

We were in a NFPA 72 training class at a hotel in Atlanta last year and the fire alarm went off in the building. A roomful (maybe 200 or so) of fire alarm installers, designers, technicians, fire marshals, etc... just sat there. I got the heck out, maybe 3 other guys went outside with me. I'd rather get out and find out it was a false alarm or drill, than be wrong any day.

The first day of the class, the hotel had a glass fire exit door locked right outside the conference room where the class was being taught. I told the manager of the hotel who didn't want to unlock it, that if the door wasn't unlocked (as per the fire code) that I'd throw a chair through it. Between a local fire marshal and myself, he got the point and unlocked it.

The main thing in an emergency situation, whether real or false alarm, is to have a flashlight and know your way out of the area. Preferably more than one way out, too, in case your primary exit is blocked or impassable.