For starters, don't go with a contractor who says it won't be a good idea that they will pop off etc...that means they don't know how to install properly. Granite can crack but doesn't scratch like other tile. As for stains, it is a porous surface so it will soak in liquids which can cause staining. using a good sealant and maintaining it will help deter this, but you have to be careful what cleaners you use. One of my friends loves the fact that her granite takes on different colors through the years as it soaks in different liquids, and I have a friend who meticulously cares for hers to ensure it never never gets a stain. I've been looking into this too as I want to replace our countertops as well so asking lots of questions to friends and doing research. One thing that concerns me is that granite is porous and so being a germ freak it makes me wonder about that...do you ever really get all the germs up? I am sure you do but still, that is a concern I have, a reason I wouldn't do all wood countertops either. Lots of people have granite tile and it works like the other response you got. It really is a long term investment, and will pay off if it is what you want do it. Just do a little homework on how to care for the granite tiles you are getting.
one thing to think about, I have a friend who went with concrete counters, they were stained and look like marble, it cost way less than granite did and looks amazing--once the sealant was on it seriously it looks like they spent TONS of money on the counters but they didn't and they are gorgeous.