Try a couple sheets, you might like it. I've only shot it in 35mm, but I find the grain pretty inoffensive. But, I'm guessing my acceptance of grain might be a bit different than yours.
I find the Portra 400NC films to be incredibly flexible. They just reformulated it again in the last year or so (400NC-3) for even finer grain. I have no problems shooting it at 400. YMMV I don't trust when others say to downrate a given (or all) film(s), since I don't know what their metering techniques is. Or development techniques for that matter.