I have two 24-105's. Prior to my first 24-105 I had a 24-70 f2.8 Sigma. I found myself spending most of my time at 70 wanting more. The 24-105 was a big improvment mainly because the Sigma was so soft. I did not notice much difference in weight. I shoot a 1DsIII with 24-105 plus flash bracket and flash. Weight does not bother me much. I do regret buying the second one. If I had it again I would have a 24-105 and a 24-70. I shoot weddings with the f4 and do not see the big deal. If I need faster I use a prime.