Tamron 17-50mm vs Tamron 28-75mm
Given that same dilemma, I bought the Sigma 17-70 os. It offers some speed improvement over a kit lens, the os and wide the 28-75 lacks, and the extra range the 17-50 lacks. It is close focusing and has very nice bokeh. Plus, it is in the same price range. Results on web sites are overall good, but you might want to check some real world results (my flickr site linked below or the 17-70 flickr group). I just hope it comes in a mount for your camera.