ahhh......i was thinking that you were the only one taking pics. i'm using a Sigma 18-250/f3.5....and it is a pretty good walk around lens, especially when carrying an extendable mono-pole.
I've never tried that Sigma, but it sounds like a good "all in one" type lens. The focal length certainly is huge. I really like Sigma lenses. I have one of their 50 mm prime lenses, a 10-22 mm wide angle, and the monster 150-600 mm C series. All of them have been fantastic performers.