I got the slip-ons to keep my feet warm while working at home. I sit next to the balcony, so I have a good breeze coming in usually and my feet tend to get cold even during summer.
They work great at keeping my feet warm, the only caveat is that they may work too well. I alternate between wearing them and slipping them off to get more of the breeze. During winter, they will likely stay on longer.
I haven't had any problems walking around with them, but they can get very hot if the temperature goes up.
All in all, they do exactly what I wanted them for!