9 out of 10 points and recommendedClear fully zoomedNot good for low light
In the L series, I only have experience with the 70-200 f2.8 and this 100-400 lens. I originally wanted the 70-200. My husband (thinking bigger numbers must be better) bought me the 100-400 instead for my birthday. This turned out to be a blessing rather than a mistake. My daughter plays softball, and I've taken some incredible shots of her and her teammates! The zoom is amazing! I can take very detailed pics of batters while I'm standing at the outfield fence! The 2 kinds of IS have been really helpful as well! I can track a runner on the bases without blurring my shots. Cons: It is VErY heavy at over 3 lbs. Get a monopod for sure. Also, once the light starts fading in the evening, this lens is useless for action shots. Would definitely recommend for daytime sports photography though.reviewed March 31st, 2012 (purchased for $1,550)
I've also used the lens to get some great shots of birds. It's a superb wildlife lens since you can zoom in and get your shots without getting too close.
I've even used this lens for a bit of portraiture. It worked well with a studio backdrop and light kit I recently bought. Of course, I had to get all the way across the large room to fit my subject. I can get good soft bokeh outside as long as I can put enough distance between subject and background.
Overall, I'm extremely happy with this lens. I AM however in the market for a good portrait lens to add to my arsenal.