Go for it gb. I'm not surprised at Ziploc, given that people sue everybody for everything. Sous Vide is not new, I have seen chefs use everything from Ziploc, to vacuum sealers, to plastic wrap to do it. You can use canning jars too.
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We have been asked many times about the safety of cooking plastic bags. The bottom line is that bags made expressly for cooking sous vide are perfectly safe as are oven bags, popular brands of zip-top bags, and stretchy plastic wrap such as Saran Wrap.
The plastic that these products are made of is called polyethylene. It is widely used in containers for biology and chemistry labs, and it has been studied extensively. It is safe. But, do avoid very cheap plastic wraps when cooking. These are made of polyvinyl chloride (PVC), and heating them presents a risk of chemicals leaching into the food.
Cooking sous vide isnt complicated or expensive. In Modernist Cuisine at Home, we guide you through the various kinds of sous vide equipment and supplies available for home cooks, including how to improvise your own setup. Check back later in the week when we share such methods using equipment you probably already own.