I’ve never used the lens before, but I’d be curious to know how fast the focusing is and how sharp the pictures are, especially zoomed in.
the-digital-picture.com, where I go first for camera reviews didn’t have much on it. However, Bob Atkins seemed to have some good details on it: http://www.bobatkins.com/photography/reviews/sigma_18-250_f35-63_dc_os_macro_hsm.html
Hope it fairs well for you! You’ll be able to compare it to other lenses as you continue to develop your camera bag. You can’t turn down a free lens though.