what kind of bulb are you using in your bathroom? I've just installed a new lighting fixture and use a cfl 65w bulb and I also replaced the regular switch with a motion activated light control. But the bulb takes a while to bright it up
Fluorescent bulbs are not always friendly to motion sensors. The fact that yours works at all, with no flickering, etc. means you probably got a properly rated motion sensor.
CFL's do have a 'warmup' time, usually only a minute or so.
Do you guys think globe light bulbs can handle the sensor?
Automatic switches use the light bulb as as part of their circuit when the light is off. Flourescent bulbs can malfunction when that minute current is running through them.