i would like to kow one thing...does redusing the f.stops (f2.8 or so) improves the quality of the picture...i mean the sharpness for a close up photo???
Also, remember if you do macro photography, the depth of field changes drastically. What is sharp in a regular photo (say f11) will be drastically reduced in macro mode (f11 becomes more like f5.6). you won't notice it until you blow it up on your screen and realize you didn't get the entire subject as sharp as you wanted it.