I've printed a ton of negatives from the various Portra films in the past 4 months. I've found that the old NC is slightly more tame in the saturation department than the new plain-jane 400, but it's a difference that is pretty much negligible. I mean, inconsequential to the point where the advantages of shooting the new film are orders of magnitude more important than scrounging around for more of the old 400NC. I do have a fairly large stock of NC lying around, and I shoot it when I'm out of the new 400 and am not quite ready to order more film just yet.
PS. the new 160 is probably exactly what you're looking for. It's my favorite Kodak color negative film.