Canon introduced this lens in 2009 to complement, not replace, the older and cheaper 100mm f/2.8 Macro.

This is the first lens to sport Canon's new Hybrid IS system, which claims to counteract linear camera shake (moving up and down and side to side) as well as rotational camera shake (rotating about a point within the lens). They reckon this is more effective at the close distances typically encountered by hand-held macro shooting. Perhaps it is, but even so it's not a 'magic bullet' for hand-held closeups; it can't deal with the inevitable back-and-forward sway of the photographer that throws the picture in and out of focus, and which can be only partially alleviated using continuous autofocus. Serious macro shooters will still want to use a tripod.

Having said that, this lens isn't all about the Hybrid IS. Test reports say that optically it's one of the best lenses you'll find anywhere. Plus the build quality is up to the standards you'd expect from an L-series lens, and if you want to use it as a portrait lens then the IS is good for 4 stops of compensation at non-macro distances.