This is actually somewhat difficult, although generally the 17-40mm zoom is an excellent lens for its price.
I wouldn't bother too much regarding individual lens design flaws, because whatever you purchase has to fit into your budget. You can still produce good photos with these zoom lenses.
@Sith Zombie: Would this 17-40mm lens be the your only lens? If so, I strongly advise to take a look at the 24-105mm zoom. It is not very expensive, but highly versatile, while the 17-40mm zoom on full-frame is a dedicated wide angle zoom, so you would be fairly limited in what you can do overall. On full-frame you may find that 24mm is wide enough often enough that the additional focal length range of the 24-105mm will do you more good than the the lost wide angle range compared to the 17-40mm lens will be an issue.
Do compare both lenses on a full-frame body, not on a crop body. On crop the 17-40mm lens provides you with a very reasonable, although not very wide focal length range, while the 24-105mm lens will be limited regarding wide angle capability, so the comparison you make on a crop body won't hold true on a full-frame body with the focal lengths of both lenses appearing to be much shorter.