Really good photo for just starting out in macro. Well done.
As was previously stated, IS doesn't help that much for many macro shots (eg you're limited by shallow dof / movement in camera, or subject. I have used the 100mm L USM IS, but to save quite a few hundred dollars at time of purchase, I went with the 100mm USM - which optically is basically identical to the L.
Using a tripod, and flash - can be important for various macro shots.