The USP of a macro lens is "1:1" reproduction ratio or life size focusing. In other words the smallest object that could be photographed that spans the area of the photograph will be of the same size as that of the sensor. So this allows the lens to focus the subject at extreme proximity (0.31m in this case) to the subject. If you have a detailed look at the lens barrel, you can find markings "1: 1, 1.5..." You get 1x magnification when the focus ring is set to 1:1 (manual focusing). This lens also can be focussed at infinity too and hence it can be used as general purpose lens too.
But I must confess that the lens is a kick-ass one. It beats the shit out of other lenses when it comes to sharpness and details. Professional macro shooters may feel, I'm a novice after reading all the problems I faced. There is absolutely no doubt about me being novice in macro, so I accept your criticism. Here are first few photographs I clicked:
Being my first encounter with the lens I assumed that it is as easy as shooting with any other lens I had. I was egregiously wrong, macro photography is a very challenging genre. The first herculean task was getting the right focus. Even the minutest movement destroys the focus, a tripod would be of great help. But the bigger problem I faced was subject movement due to breeze. I was trying to shoot a blade of grass with water drop on it and it took nearly 5 trials to get a shot with desired focus, either I moved or the subject moved when I didn't. I was so down and dirty when I was shooting the grass that I felt every inch of my body will suffer from RSI if I shoot more macro.
At such extreme close-up the Depth of Field is very limited and hence the aperture needs to be closed down to a great extent. For such small apertures, your shutter speeds will not be hand holdable which results in many blurred photographs.