I am not particularly brand loyal, but do have some preferences. I'm usually fairly satisfied as long as I get a quality product. DH and DD are another matter.

DH must have:

Dove original version bar soap
Right Guard spray deodorant
Red Baron Pizzas
Hefty's big black trash bags with the pull cord thing to seal

DD must have:

John Frieda hair products
Degree antiperspirant
Cocoa Wheats cereal in winter
Strawberry Poptarts in summer
Green Giant frozen vegetables

So far I guess I have been lucky as I've managed to get a small stockpile of all of these things for very good prices matching coupons to sales. DH has stated he will give up and use other brands if they're free. Can't wait for DD to get out in the world on a budget and see how she feels about her brand loyalty then.