Great shoes, but not very durable!
I run 100 km per week on average. For a long time, I've been a very satisfied On Cloudsurfer user. However, ever since I tried the On Cloudflash I've found a better shoe:
light, elastic and less prone to stones getting stuck in the soles. Great for long distances. They outperform the Cloudsurfer easily in durability of the bottom of the shoe.
On the negative side, most On shoes don't have the regular 700-800 km lifetime as other brands. My first pair of Cloudflash shoes lasted only 425 km. The "incredible light mesh" is torn on the top side, most likely because of the continuous friction. One should be ready to replace them more frequently.