I first calibrated it to both my cameras (5dmii and 7d) using lensalign and the microadjusts. But I'm sure you made similar calibrations so perhaps you have a bad copy?
The OP has a 1D MkII (and had a 350D before that) - no AFMA.
Just got a new 17-40L from a local shop (along with the 70-200mmL IS). The focus on the 17-40L seems off... it is worse than what I remember on my 18-55 kit lens. I know not scientific enough... but having tested the 70-200mm on my 1D2, it seems sharp enough as I would expect any L lens to be, and I am not comparing the 17-40L to the 70-200, but it really does not seem sharp enough.
In the center with the aperture wide open, sharpness is similar between the 17-40mm and the 18-55mm kit lens, but away from the center the cheap kit lens is noticeably sharper. In the f/5.6-f/8 range, they are similar across the APS-C frame. At 17mm on FF, the 17-40mm is soft in the corners even stopped down to f/8. With your APS-H sensor, the corners should be soft, but the center should be decently sharp. Looking just at the center of the image, sharpness of the 17-40mm is pretty similar to that of the 70-200mm f/4L IS.
Read the article Flake mentioned - here's the link
. Another article (also by Roger Cicala) is also worth a read - how to test a lens
. It's important to distinguish between AF errors and softness - manually focusing is usually the way to do that.
[I have it ona 1.3crop body so the corners are not even an issue for now. should i get a Tamron 17-50 f2.8 instead or replace it with another copy of the 17-40L?
The Tamron 17-50mm projects an APS-C image circle - it will vignette heavily on APS-H.