Hello Matt,
Vivitar 17-28/f4 is one of my favourite lenses. For a 17mm lens, the price is inexpensive and the result is not disappointing at all.
So far when I shoot at open wide in 17mm with lens hood attached, there's always a soft vignette around the frame.

You can check one of my sets in flickr that using Vivitar 17-28 http://www.flickr.com/photos/jalijal...th/5929890457/