I have one
like this one- it's handy for keeping things cool while underway in the car, but it doesn't chill as cold as an ice chest does. This because they're really "heat pumps", so won't reduce temps much below about twenty degrees of ambient temperature. I also bought an adapter that lets one use it off 110v for trips where power will be available at destination.
Here's a tip:
Since cooling is related to incoming air temp., strategic placement near an onboard A/C vent works wonders.
I like the "keep warm" feature, too- handy if one goes to a lot of potlucks!