I have one of this lens and I can say it give decent photos. A lot of people are selling it online with unfilled warranty and i guess you can get it from then at around $300 or so. I got mine for $350 though. It give a distince difference from the kit lens(28-90) cos I'm using the kit on half roll then swopped over to this lens and finished the remaining roll. Very quiet and very fast. I never use my kit lens ever since.
This lens uses 58mm threaded filters. Yes, it gives decent results between 28 & 105. At both extreme ends, it seems to be a little soft. It can also be a good thing to be soft at 105mm for portrait shots, but not at 28mm. IMO.