I bought a Waeco some years ago – I'm pretty sure it was a Choice recommendation, but it was also on sale.
I use it almost exclusively just for getting the groceries home from the shops, although that is largely because I have done very few trips away in the station wagon since buying it.
I also used to use it when defrosting the downstairs freezer, running it off an adapter (240vAC to 12vDC) but now I have upgraded to a frost-free model the Waeco never leaves the back of the station wagon.
It can be run at freezer temperatures in the station wagon as well, but apart from proving the battery could pull it down below zero I have never run it that cold in the vehicle, settling for somewhere around 3°C as the optimum for the mix of stuff from the supermarket (or from my kitchen fridge when I am off on a trip).
I put in a mixture of fresh and frozen food, and fresh drinks -- I haven't caught a fish since owning the car fridge, but were I ever to wet a line again I imagine it would be ideal for keeping the catch fresh 'til I got it home to the pan (and I wouldn't be buying ice for the Esky!).
The fridge always has its switch set to "on", but I only plug in the lead to the cigarette-lighter socket when I want to be running it, and I usually try to throw a freezer brick in to help chill it down when I'm not going to be driving very far before doing the shopping.
The one gripe I have about it is that the lid has slightly warped over the years so that it will no longer clip shut, but my thermometer says it is still able to hold the temperature below 4°C – cold falls and all that.