I have not written in a while so now's a good time to mention I am thinking of parting with my excellent 17-55 f2.8. The lens is a beautiful piece of work for a zoom but it lacks in some ways that are beginning to irritate me. For one, I wish it were sharper. I know it is very sharp for a zoom but not enough for me. Secondly, I wish it were faster....But I did buy it knowing it has the f2.8 limitation. And thirdly, it is designed for crop sensors. I am beginning to consider going to full frame.
So, I think now is the time to upgrade to some fast primes and make those the core of my lens arsenal.