For an 800 speed film, I've found it to be pretty good. The Fuji professional films (NPZ, used to be NHG II) have less grain even at 4x6, but cost more. With either film, a good 400 speed film will beat any of them for grain. I used a great deal of 800 Press, NHGII, NPZ, and even the Fuji Superia 800 ( Acts just like 800 Press, as far as I could tell) a few years ago.

The Kodak consumer 800 speed films are total junk in comparison to any of the Fuji films. I haven't used Portra 800, I don't think it was out then. I actually have the need over the next month to shoot basketball in dim gyms, and will probably use Press 800 or NPZ.