The barrel distortion at 17 mm is about 0.8% (noticeable but easily fixed in PTLens). It lessens going to longer focal lengths and is not noticeable (0.3%) at 28 mm. Over that both barrel and pincushion is not noticeable (under 0.3%). The lens performs over all very well at f/2.8 to 11.
I've been using the 17-55 all year and i just love it on my S3 /D2X , any distorsion is easily fixed in Photoshop , but if you keep verticals away from the very outside edges you hardly notice any .
But here are 2 images with verticals close to the outside .
number #1 is just to show the barrel distorsion
Looking at Brian's barrel photo I'm really impressed with the lack of wide-angle distortion with this lens. A wider lens would have had the barrel at the left edge of the upper row stretched out into an oval. This lens kept the round shape very well.
Most folks focus on barrel & pincushion distortions -- which are at least correctable with PP -- and pay little attention to the wide-angle distortion of a lens, which cannot be corrected at all. A poor wide-angle lens will stretch objects at the edge of the frame far beyond normal perspective distortion. Short of going large format with primes, there's no way to avoid this. But some lenses are just bigger offenders. This one is looking good!
The only sweet spot I ever found with mine was right in the middle!
It has seriously been the worst Nikon lens I ever had!
Hope you have more luck!
Cheers,
Jasin.