My mom recently found out she is allergic to milk and yeast (as well as a host of other things...) She has drastically modified her diet but one of the things she really misses is cheese - grilled cheese sandwiches, cheesy pasta, maybe even pizza if I can make a crust with no yeast...
Most of the vegan cheese I've found has casein added (what's the point of that??) or has yeast in it. We tried one brand from Giant - Rice Vegan I think? - but really disliked the taste.
I haven't found a cheese sub yet that tastes much like cheese.
We use these for grilled cheese and egg sandwiches. I have made mac and cheese with no cheese subs, just nutritional yeast, and it tasted pretty good. Mostly a "white" sauce of flour, margarine and chicken broth. For pizza, I mostly use nutritional yeast in the sauce. It's different, since there's obviously no cheese, but it does taste a bit cheesy. We do have one brand of soy shredded cheese that's ok but not great. I can't remember the brand right now though.
I have never understood why most cheese subs have casein.