i do agree with you
there is a certain haziness over the pics when i
use f2.8.....but i gather the 24-70L has the same
thing too although slightly better
interestingly , of late i have been trying NOT to
USM too much that cause some grainyness
yes, pics looks softer nowadays
maybe i should go back to those old USM settings
Yes, you should go back and use USM or smart sharpening. This recaptures some of the detail blurred out by the antialiasing filter on your camera's sensor.
Be careful, it's easy to over-sharpen, I've done that mistake many times before becoming conservative enough (how you use USM/smart sharpening varies from image to image, and print size to print size, and of course it's different for viewing on web, too).
But I guess part of your problem may also be an unsteady hand, there seems to be some sort of camera motion blur in several of the pictures.
Your pictures aren't helped by aggressive JPEG compression, either, try using at least JPEG "high quality".
This is an example of a shot at 24mm f/2.8 with the 24-70L, EOS 20D, 20% pixel size, USM 0.2 px radius, 300%, JPEG "high quality" from "save for web":
There are still slight JPEG artifacts, as you can see, but otherwise, the image isn't that