Resumen: In short, this is clearly a very impressive lens in all respects. It is also keenly priced. Yes, for only about £150 more you could buy Canon's very capable 24-105mm f/4 zoom, which is a better all-rounder, but the 100mm macro is not meant to be an all-rounder: it has been conceived for one specific...
Conclusión: Just occasionally a lens turns up which delivers such implausibly good results in our studio tests that I have to go back and repeat everything, double checking all settings to make sure I haven't done something wrong.
A favor: Superb optical quality, Fast, silent, and accurate autofocus; full time manual focus, Highly effective image stabilization (for longer subject distances, at least), Solid build, including dust and water sealing
Contras: Hybrid Image Stabilization still not particularly effective at macro distances, Precise manual focus at 'portrait' distances slightly tricky, Very expensive compared to non-stabilized alternatives
Conclusión: This is an exceptionally sharp macro lens but with a price tag to match. It’s the first Canon macro lens to incorporate image stabilisation, though with macro photography depth of field is likely to cause more problems than camera shake.
Extracto: This 100mm lens from Canon costs around £779 and provides life-size magnification at its closest focus, image stabilisation, weather-sealed construction and an ultrasonic focusing motor. This is not the only 100mm Macro lens Canon produce.
A favor: Build Quality, USM focusing, New Image Stabilisation system, High resolution, Useful Focus limiter switch
Contras: Supplied lens hood is a little deep for use at close distances, Focus breathing can make composition tricky