Surely using less resources in any machine is useful as it leaves more for your actual app to use. Admittedly you might get _more_ benefits from having it on bare metal, but on the other hand the OS using 10% less ram (for example) on a small VM might make more of a noticeable difference to your app.

Personally I prefer having cloud machines to bare metal machines simply for my time being saved in doing things like firewalling them or load balancing. But then my personal time is more precious to me than a few extra £ a month out of my pocket, so that's an active choice I make. CoreOS (& docker especially) seem pretty neat, regardless of where I want to run them as it were.

Perhaps you're right though, I've not used CoreOS in anger yet so I don't know specifically. :-)