I do not see why this lens is so unpopular, it has many advantages over the 24-105mm and other lenses.
- Lightweight and small. A mere 600 grams. It's the same size as crop standard zooms like the 15-85mm and 18-135mm!
- Lowest distortion. At 24mm it's just 2.4%. It beats even the 24-70mm II which comes in at 2.83%. Trounces the carnival mirror like 24-105mm which comes in at 4.28%.
- IS. It has 4 stops IS, beating the 24-105mm 3 stop IS. And unlike the 24-70mm II 2.8 which can't realistically be shot below about 1/125, you can shoot the 24-70mm f/4 all the way down to 1/10.
- Sharpness. It's noticeably sharper than the 24-105mm. See this comparison: http://www.slrlounge.com …ens-wars-series-episode-9