Most definitely. Though, you can be part of any Google Group if you just have G-Mail. Actually I think you might be part if you just have any e-mail.
I was first against it, but then I said whatever. After using it a bit, I realized it's not half as bad. I came to find it very intuitive. You even have a few nice small features like setting it up to send you an e-mail when somebody posts a new thread or uploads something. So you don't only have a discussion group, you have an online repository as well. At an earlier project we used Dropbox, but I found it a bit clunky so Google Groups was kinda exactly what we were looking for, lol!