Well I suppose it has all been said before. Got one copy, hopelessly soft (the otherwise cruddy kit lens on my 30D was sharper), exchanged for another copy, same problem. Other lenses on my 30D are fine so it was not the camera at fault. What a shame because everything else about the lens seemed great.
So if you have the time and persistence to try and try and try again, or to send off a brand new lens to Canon in the hope that calibration will maybe solve the issue, then this lens could well be worth the hassle...but sorry, I don't have the time or inclination to go through all that. I feel justified to rate it low based on what I saw, not on what a "good copy" of this lens might be capable of. Maybe the "L" in Canon lenses stands for "Lottery". I didn't win.