Hi Orestis! I don't own the the 100mm but I have a friend that does, he laments not getting the L Series of that lens. The reason being that the standard series does not have Stability Control and when he's taking macro shots, if the camera is not attached to a tripod its hard to keep it steady. There are some good deals on gumtree for a L Series 100mm between $700 and $900.
Hope that helps
