The 17-40mm zoom may not be the very best of wide angle choices, but it isn't so bad either. I primarily shoot wide angle primes (14mm L, 17mm TS-E and 24mm L), but sometimes the need for versatility makes me pick up my 17-40mm zoom and no it doesn't kill me to use it, not on a 1D-X nor on a 5D Mark III.
Actually the 17-40mm zoom provides a much nicer zoom range on full frame than it does on crop, so yes, this lens will come into its own on a full frame body. It has not been designed for crop cameras. I expect you will be happy with it despite its flaws. In case you are desperate for better optical quality, you can still follow my route and collect wide angle primes .
When I use my "17-40mm F/4" on my 5Dc as if it was a "20-40mm F/8", most of the concerns about sharpness (and distortion) disappear .
BTW, F/8 is not a weird aperture for a mostly-landscape-oriented lens.
Italian amateur. Gear: i) 6D, 70D, 10-18 IS STM, 24 2.8 STM, 55-250 IS STM, 17-40 F/4 L, 24-105mm F/4 IS L, 70-200 F/4 IS L, 35mm F/2.0 IS, 50 1.8 STM, 100mm F/2.8 IS L.
ii) Wife: G12
iii) First Daughter: 1100D, 18-55 IS iv) Son: Canon PowerShot SX510 HS v) Second Daughter: Nikon L21