There are some real advantages in switching into manual mode. I spend may of my early days in Av (where I controlled aperture and the camera set the shutter speed) and Tv (where I controlled the shutter speed and the camera controlled aperture). It wasn't until I shifted into manual mode that I started to see different possibilities.
Using manual mode takes a little more time but offers fantastic creative possibilities. On the Canon digital camera that we use at Individual Pixel Photography, this means moving the main mode dial to "M" and then using the forward command wheel to adjust shutter speed and the rear command wheel to adjust aperture (whilst also considering the ISO you need to dial in)
It took me a while to learn some of the shutter speeds i needed for different creative aspects, and how to compensate for the exposure but eventually I got to the point where I knew if i wanted a pin sharp freeze frame on cars, motorbikes or animals then 1/1000sec was best, and if I wanted to freeze mountain bikes then 1/500sec was about right.
In some situations you want to show the motion of a moving object by blurring the background (or an element of the frame). This is especially true in concert photography where you want to show the motion of the guitar players strum or the drummers sticks. Here, I started to find that 1/125sec was a good speed for this