I was so pleased with my Gel-Nimbus 15 that I didn't even consider buying any other shoe. I wish I had. Either the cushioning in the 17 is not as good as in the 15 or I received a defective pair. I can't run more than a mile before the ball of my right foot begins to hurt. I never had any such pain or problem with the Nimbus 15. In fact, the only other occasion in which I had a problem with pain in the ball of my foot in the many years I've been running was with a pair I purchased just before buying the 15. The cushioning of the 15 resolved the problem immediately. I've run in the Nimbus 17 four days. The problem with the 17 appeared the first day I went out and has been a constant since. Very disappointing.