Nice photos, Aphex. I bought a Sigma 28-70mm f/2.8 a couple of weeks ago and was pretty disappointed with it. Not that it isn't a decent lens for the price, but the focus was really soft at f/2.8 70mm and in low light the AF is almost useless. In bright light it's a good lens, but when you buy an f/2.8 you're most likely planning to use it in low light conditions.
Oh, and I really liked that first photo, full size. :thumbsup: