I just got them on my Stealth last week for this week's skiing road trip! Honestly pretty impressed with them so far. Efficiency stayed pretty much the same from what I remember getting in my previous road trip with the OEM 18" wheels, high 300s while driving at around 85 mph in below freezing temps.
Their snow performance is pretty impressive, from what I can tell, drove down snowy mountains without issue, at reasonable speeds of course. Was also able to use slip start to get unstuck out of a parking spot on the first try.