Thanks for you kind comment. After saw the photos posted here, I also found my photos quite soft.
Here is my setup:
Camera: Canon 30D
Len: Sigma 150mm macro
Flash: 550EX
Photos:
1) ISO800, F10, 1/100s, FE -2
2) ISO800, F14, 1/100s, FE -2
Hope to learn from you all! :D