Make sure you mix them in your soil quite well if you are using that much. It can be too much of a good thing. They can serve as a watershed and impede the water from soaking into your soil. The earthworms they attract will benefit the soil more so than the grounds themselves. Anything organic especially oak leaves will help too.
Another plus is that they are great to ward off scale and mealy bugs (if they are fresh)

Good question. Here is an article that answers it.
john

Here is a link that might be useful: Coffee grounds

Thank you so much John. That is a great article! I guess the grounds really are a good thing!

You're welcome. I just use what we make at home, (no Starbucks here) but I mix in the crushed egg shells and chopped up banana peels. Potato peels would be good too, (for the K) if my wife would ever peel one. ;>)
john