I bought the On Clouds after running in Salomon, Saucony, and Merrell Trail. The Salomon and Saucony were stability shoes which I didn't need but as I wasn't running too many km it wasn't a problem. I ditched those because I didn't feel I could run far in them, but had no idea why I felt that way. I read about the whole minimalist shoe, faster cadence, etc trend, and decided to try the Merrell Trail as a minimalist zero drop shoe. These didn't work me - felt sloppy on my foot, and no cushioning in the landing. Even though I run more forefoot and mid foot, occasionally I heel strike, and these just made my legs feel tired when I started to increase mileage. A friend suggested New Balance (last year's model) and On Clouds. After a few runs in the On Clouds I was hooked. Every so often I'd try the NBs again and it was like landing in sludge. The feel of the Clouds is different - the shoes are very light, the sole cushions my metatarsals, and gives a 'bounce' when the heel lifts in toe-off. This is not a sludgy sinking-to-sponge feeling like the NBs or the Salomons, nor the hard feeling of silicon as in the Saucony, nor the flat resistance of the Merrells. I won't go back to a traditional sole shoe after wearing these. I run on average 70+ km / week in these most months - I ran 1600km total for the first two pairs before sore legs reminded me that I needed to buy a new couple of pairs.
However - On Clouds don't fare well on trails with small pebbles, nor trails with slabs of rough cut stone. For these trails I found the Cloudventure a much better solution - the On Clouds pods mashed after several fast downhill runs (around 4-5km in length) on rough cut stone trails. The On Clouds are best on road, pavement, dirt, track or grass. The Cloudracer is terrific on track, I've also worn it on road. These shoes are minimalist in the sense of heel-toe drop, and overall weight, and are neutral not stability. On do make a few stability shoe options, as well as options for heavier runners (even when running fully laden with vest and water bladder/bottles I weigh in at less than 55kg).
For me the shoes are a running shoe - but the springiness in the shoe is popular with people for all day standing activities as well. They have a useful 'find my shoe' calculator on the site.
I hope that helps. If you have any other questions, please ask.