I own a 16-35mkII and it worked perfectly with the 1Dmk3 I had.
After I replaced the 1Dmk3 with a 5Dmk3 the 16-35mkII wasn't good enough anymore: the off-center unsharpness is just too visible. I bought the 17-40 which is a lot sharper (but obviously lacks the F/2..
I really like the 16/17 to 35/40mm focal range, so I'm really hoping they are going to release a sharp 16-35mm F2.8. The 14-24mm F2.8 sounds as a nice addition to the 24-70mm, but for the type of photography I'm doing I'd rather use a 16-35 + 70-200mm combo.
Just my 2 cents.
You're the first person I've ever heard say the 17-40 is sharper than the 16-35 MkII. I'm going to go further and say you outright had a defective copy of the 16-35 because every tester says the 16-35 is sharper and my own experiences have reflected that.
If I recall the charts correctly, the 16-35 is sharper, but has a fairly dramatic drop at the edges. The 17-40 has less of a change from center to edge - so it the perception may be less pronounced.
That or yeah, crappy 16-35 copy. But even then, I recall most of the sharpness is in the upper end of that lens - which can be handled by far better lenses. A 14-24 or even a really good 16-24 would be preferable, since just about everyone has 24 on up.