Top 3% or so at Northwestern.
I interviewed at 14 firms from Monday, Aug 10 to Wednesday, Aug 19. All the firms were V50 or better in northern California. So far I've gotten 6 callbacks, 1 ding, 1 email saying they're interested but won't be making callback decisions until next week. Two other firms told me during the interview that they wouldn't be making decisions until early September. So that leaves four firms where it's been long enough that I'm guessing there's a sad letter in the mail for me.
All 6 callbacks were a phone call from my interviewer followed by an email from the legal recruiter.
The calls came 1-4 days after being interviewed. The mode was probably 2 days.
I had two interviews that I would describe as "really horrible" that I still got callbacks from. Therefore, based on this overwhelming anecdotal evidence, I'd say grades are still the most important thing, no matter what, in the OCI process.
Hope that helps!