The Nike Air Zoom Structure 25 has a higher stack of softer, springier foam than any previous Structure. While the 24 was not technically classified as a stability shoe, it was very much in the same vein of a moderate cushion, stable, durable, versatile running shoe that the Structure line has always been. The 25 seems to be following the trend in the running shoe industry of more, softer, springier cushioning. It is more in the same category as the Saucony Tempus now (and probably also the ASICS Gel-Kayano and Brooks Glycerin GTS). It is still comfortable, stable, and fun to run in, and can soak up a lot of miles. With the added cushioning, softness, and weight, it is a less versatile shoe than the Structure has historically been. I don't think you would really want to use it for speedwork or racing, whereas previous versions have always handled those things fine, despite the weight. It really seems like the shoe companies are trying to force us all to diversify our shoe lineups, so that they can sell us more (and more expensive) shoes. Despite that complaint, the Structure 25 is still a great shoe and one that I imagine long-time fans of the series will still enjoy.