I used 5 gallon DWC coolers last year, I think it kept the tomato roots too cold all day actually. Didn't turn out to well, because I was too busy really.. and I should have been supplementing to prevent the inevitable..
This year I went back to coco. I always wanted to try out Larry's rain gutter bucket system too. Net pots in the bottom of the buckets, that sit on and in the gutter, with a float valve. Simple
I'll be re-using all my old 1 liter\gallon bottles, making custom recipes, and printing my own nutrient labels soon enough!