I am looking at getting something to replace my kit lens. I want something sharp and fast. I mostly take portraits, pictures of my kids on the go (for which I find the wide angle very useful for playgrounds and indoor shots), and landscapes. So basically I want a muti-use lens. I wish that I had the money for a prime, but I am hoping to keep my budget around $600 (but willing to go higher). I am also looking at the Sigma 17-55 f2.8 and Tamron 28-75mm (I like the idea of the zoom, but the down side is that I loose some wide angle).