desertratt, that totally makes sense. Really, basic troubleshooting: if marks are not consistent, you can exclude the camera and/or lenses. I don't know why I needed to air it out here in order to realize it...overall lack of photographic confidence, I guess. When I bought the lens, the store was relocating and they had these sitting around in plastic boxes, they were sold 'as is' so I always assumed that there will be something wrong with it and not knowing how to evaluate the lens myself, here I am...I know it's a low end lens anyway but I just find the results I got with it quite blah. Needless to say that my exposure skills largely contributed to it.
thanks again!