A bit more information if it helps others:
As mentioned in a previous post, I got the CGS this year as a first-time applicant with a score of 17, committee 4. At the time of the application I was finishing up my MA, had two submitted/under-review publications (one for the "short pieces" section of a major journal and one for a very small conference proceeding), and 4 conference presentations -- two small, student-run ones and two professional rather than academic. Other applicants from my department had way more research contributions and I thought this would affect my chances. So I think that research background counts, but isn't a make-or-break deal -- it can be made up in other areas.
BTW, it turns out my MA supervisor (who's also our program director) has known for a few days, but wasn't allowed to tell me anything!