If you have line of sight and more than 8 devices then the One is a great buy, if you can find one to purchase. There are plenty on Craig's List, with no buyers, in Vancouver selling for $100+. Personally I don't know their condition.
I, personally, am not enamored with the ONE because of its lack of actual physical red, blue etc buttons, which I usually map for other convenient uses.
I have 8 devices and love my 650 and 900. Although I have line of sight I prefer using the 900 because I hate pointing the remote for a full minute or two. But that's my personal preference. The main drawback, to some, is the 900 does not do sequences which I never use.
I briefly owned a Ultimate and Smart. While both worked very well I found the layout on the Ultimate takes some getting used to. Thus I kept hitting the screen accidentally. I'm certain if I kept it longer I would like it. Personally I find the hub based new Logitech remotes temperamental with frequent disconnects from the router. The Smart hand held has very small buttons, no backlight, help feature but price wise its probably the best bang for the buck, if you get one on sale and 8 devices, and like using another ipad/android hand held. Still has flaky disconnects of the hub.
I find that remotes are very personal.