Even aintitcool.com's Harry Knolls put it down a bit, saying he saw a recent 35mm screening and it wasn't as grainy as the BD. I tend to think that the grain was probably there but it's expected during a real film screening and doesn't stick out. However, on BD, some expect a glassy smooth image...
It's funny to see how diametrically opposed the feedback on the Ghostbusters BD is here compared to the feedback on Amazon. Some reviewers are calling it the worst blu-ray they have ever seen. It just shows how film grain adverse some people are.