Not many vegetarian foods are as high in protein and low in carbohydrates as quorn is. Adding quorn to your veggies increases the % of protein (useful if you are on a Zone diet). It also has a much more interesting texture than tofu.

My local supermarket now has a whole shelf of quorn and quorn products.

I've eaten plenty of it and the only problem I've had heartburn once or twice.

It really doesn't bother me that if its made in a vat, probably so is everything else you eat, apart from fresh vegetables.