They say f2.8's are the way to go but that all depends on what you do. Being that I cater to both Photos and Video, The 16-35mm f2.8L II USM has barely gotten any use because it's lack of IS and being able to shoot at 1/5th with the f4L IS has given me much cleaner images than the f2.8 ever could unless I have time to setup a tripod. Now keep in mind, my experience may be a bit different because I also shoot video but I love the f4L IS so much I am selling the f2.8 and my 24-105 as well. My average range is around 16-35 so this lens fits perfectly for my wide angle needs for both Photos and Video. If it was f2.8 it would be a perfect lens but IS more than makes up for the stop difference.
This lens deserve more credit, It's sharper, Less distortion, cheaper and the Image Stabilization is insane!

. The best wide angle lens I ever own.






