i bought that lens about half year ago as replacement of my kitlens - tbh its not that big difference image quality wise...so basically you get some bigger focal length range and f2.8 at wide end, which is nice...
dunno if its just my piece (wouldnt be surprised with my luck on lens), or if each sigma acts like shit sometimes? http://don.vn.cz/temp/repo/sigmasucks.jpg
EDIT: actually when browsing my photos from last rally, i took most of the pics with that lens, so you can check yourself - (take a look at exif and whatever is below 70mm is taken with teh sigma) http://rallyphotos.cz/photos/vyskov09/
dunno if its just my piece (wouldnt be surprised with my luck on lens), or if each sigma acts like shit sometimes? http://don.vn.cz/temp/repo/sigmasucks.jpg
EDIT: actually when browsing my photos from last rally, i took most of the pics with that lens, so you can check yourself - (take a look at exif and whatever is below 70mm is taken with teh sigma) http://rallyphotos.cz/photos/vyskov09/