...I have found is the insights and inputs from the other people participating!

I agree, anytime one does something with other people, sometimes one is pushed or pulled along, or one withdraws entirely. But if you get in from the beginning, and often when it is a reread of a book (I personally haven't participated in a Group Read where it was my first read of a book), I have just appreciated a deeper understanding of the characters, of the plot, of the society of the time so the import of certain things in the novel... it can really be an eye-opener! I've found it secondary having my share of the conversation, although it always is nice when someone appreciates points that one has made.