I'm getting mixed results with the kit lens that comes with the Rebel XT. Some shots are sharp and well-focussed. But several of the outdoor shots, with plenty of light came out soft, out of focus and/or washed out. I shot most of these in the Av mode, and they were shot at many different aperture settings, so it's not an issue particular to the extremes. I did use a UV filter and a circular polarizer on top of the UV filter, both made by Quantaray. I can't decide if the issues are related to my skills, the lens or the filters. If it's the filters I can quite easily validate that by removing them and shooting the same scenes, which I might be able to do in a few more days. But I suspect it's not the filters.
Here's an example...