I've found my study group to be very beneficial.
As a 1L, it's difficult for me to tell if I "get it", or to gauge how I'm doing relative to my classmates. Discussing things, even the stuff you'd categorize as gossiping, is important. It helps to know that I'm not alone in my experience. I could go on and on about how those discussions are important, especially in our first semester as we're figuring everything out.
Secondly, isn't discussion a critical part of what happens in the classroom? Being asked questions? Defending and explaining our answers? More than once I have found, through discussions with others, that I misunderstood something. Or found a flaw in my argument. Those conversations have shaped the way I tackle my reading assignments as well as my legal writing papers.
Third, study groups can help keep you on schedule. It would be tempting to fall behind in my reading- the exam is a few months away, and class participation doesn't count for much. So what's the big deal if I'm not 100% caught up on my reading? With a study group that expects me to have read the material and be ready to discuss it in a small group, rather than a large class where I may or may not get called on, I am much less likely to let things slide. My hope is that at the end of the semester I can focus on reviewing material rather than trying to read it for the first time.
Fourth, I think that the relationships you develop with your study group are going to be beneficial long after you leave school.
Law doesn't exist in a vacuum, so why should you study it in a vacuum? In practice, you'll have to work with others and still be efficient. So why not start picking up that skill now?
And finally, who ever said work can't be fun? It's possible that this isn't the most efficient way to accomplish some of these goals. But at least you're accomplishing them. To use your analogy of the elliptical trainer... the treadmill might be the more efficient piece of equipment, but that is of little help if people dislike it so much that they never use it. If a study group gets you to study even a little bit more, then that seems like it's a good thing.
Study groups are beneficial for a lot of people. You just have to make sure that you're getting something out of them.