I use this lens as my main walking-around lens on my Nikon D5000. It is sharp wide open and tack-sharp from f/4 on. On the DX body it is sharp corner-to-corner and has no noticeable vignetting. Unlike my Tamron 90, there is no LoCA at all with this lens that I can see. I have had absolutely no problems with the focusing on this lens, even in very dark indoor conditions. It's BIM is fast enough for anything that I shoot (I don't do sports shooting, so some folks will have more rigorous requirements in ths score than do I) and adequately quiet for my purposes. Some folks find the lens to have a yellowish tinge, but I don't notice that. It focuses closely enough to satisfy my routine close-up needs, although it is not a marco lens. But for filling the frame with a flower blossom, it is all that you will need.
The one thing that I find suboptimaly about the lens is its pronounced barrel distortion at the wide end. It is simple barrel distortion that cleans up easily in pp, but I find that I want to remove the distortion with this lens at wide focal lengths more than is true of any other lens I own. If you are willing to do that as part of your post work-flow and use a cropped sensor camera, you'll probably be very pleased with this wonderful inexpensive standard focal length zoom.