I have a green 55L one. It is beautiful and enormous 
Today is its first outing. We are off camping for 2 weeks and it is full. I pre-cooled it as previous poster with frozen bottles of water, and then filled it last night with frozen and chilled food plus various gel packs etc.
Because I'm sad I have put my fridge thermometer in too, and am trying to resist peaking in to check the temp 
But after 24 hours pre-cooling with 3 frozen bottles and some cushions to fill up the space, it was the same temp as my fridge, so that's a good start. May update that later. I'm hoping to have to shop and also re-freeze our ice blocks less frequently - will let you know how I get on.