PhotoZone reviewed the lens here
and it got a glowing report. Unless you are using a full-frame camera the crop factor implies that you will need to use shutter speeds of around 1/200th of a second or faster to avoid blurring due to camera shake (or use a tripod) as, of course, the EF 100mm f/2.8 Macro USM
doesn't have IS.
I've been scratching my head trying to work out if this post should have been in the Canon forum and have decided that it should as the Flowers and macro (close-up) photography
forum has the subheading "Share your tips or ask questions about flower and macro photography here". I've left a shadow behind so that you can still find your post. Hope that's OK with you.