The documentation is all over the forum, in the "Getting Started" booklet, and on the website. They are not in one place. Also, they often conflict. At least one figure shows a connection that is different than the connection in the code. The DHT sensor needs a second parameter that is a "0" or "1". The only place this is documented is in the code, itself. It would also be good to show the user how to update using git.
The documentation for the Grove Pi library is ???. A listing and description for each element (DHT, for example) would allow use beyond the nice examples given.
The inclusion of non-Grove Pi code is confusing to the novice user. Since the appeal of the nice Grove Pi is the ease of use, the documentation should be tailored to users that are easily confused.
I've enjoyed the hacking, and have learned much from struggling to get sensors to work on A+, B+ and B 2 versions of the Pi. But the casual user need one stop shopping for documentation, and that documentation should be 100% accurate.
I must say that the little booklet is nice - it's just that it doesn't all work, depending on what firmware and Grove PI software release you have.
Don't get me wrong: I really like the product, and I've got it into pretty good shape. But I'm an electrical engineer with a lot of coding experience.
Hope this is constructive and helps!