I love google docs. I don't think I would have managed to get through all of the group work that we needed to do in the teaching program without google docs. I know that group work in school is often difficult with students who have different schedules, maybe sports after school etc and who have difficulty getting together with their groups. Using google docs allows students to do work more easily with each other without having to get together in real life to exchange ideas.
I've also used google slideshow many times for projects where we need to present something. Having google slideshow means that the roles can be distributed more evenly, you don't need to have one person creating the powerpoint, everyone can contribute to the slideshow their own material. This allows for everyone to do a part of the actual learning.
I've never used google forms but I can see it being a really great tool to communicate with students and parents. It might be great to use for teacher-teacher relationships and for Pro-D communication.