Having used ON for a few years, the Cloudflow has ironed out a few of the minor niggles that I'd had, and I think it's a near perfect shoe. Super light, super comfortable and a great looking shoe (not the most important criteria, but there are a lot of ugly shoes on the market). Am a midfoot striker, with a short stride, and I do notice the weight/comfort benefit versus an alternative brand that I used for distance running.
Am running two pairs in parallel, and using them for pretty much everything (short and quick, and longer, slower runs) including running the Chicago marathon a couple of weeks ago. I still use a couple of old pairs of ON Cloudsurfers for really wet weather, as once they get dirty it's pretty tough to get them looking clean again.
The remaining issue I have is the 'sock like' inner....it's undoubtedly comfortable, but am not so confident about wear around the heel. Am a heavy-ish runner, and that's one area where I'd like to see a more robust material. Despite this, am a satisfied customer.