I'm not really a brand-centric type of person. If one brand is cheaper than another, I will often substitute the lower priced one, unless I've had issues with the cheaper one in the past. There are things I won't substitute, though. I really prefer whole milk to skim milk, or even 2% milk, and I will pay a little bit more for that. I also prefer butter over margarine, and there are specific brands I like better, although if there's a large price difference, I'll buy the generic butter. Are there certain products you just won't substitute, or does it all come down to money?