Sorry if this sounds very fundamental... But its just tat i'm not quite sure when is the manual mode essential/useful. Most of the time i'm using av/tv on my cam... and i find that this satisfies most of my shots. If i need to tweak exposure, most of the time i just use the exposure compensation.
So just wondering, under wat situation would the manual mode be useful...since shutter speed and aperture are related and fixing one would mean the other value is more or less fixed, in order to get a correct exposure.