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Here's two relevant Portra 800 samples. Note that these are both 800-2, and not the newer 800-3, which should be a bit better.
First is a boring test shot on 6x6, scanned on a minilab.
Portra 800 0 by ezwal, on Flickr
Second is 35 mm (sorry, it't not MF), but, if you click through to flickr and select the original size, you can get a sense of what the grain looks like on a 4000 dpi scan. A drum scan should be better than what I got too on my Coolscan.
al by ezwal, on Flickr