Kodak Portra 800 is my favorite film. It's the perfect film for me as I like to experiment with the look of my work. I admire other photographer's consistency, like Johnny Patience & Bijan Sabet. They make Portra 400 look so yummy and their consistency is remarkable. But I am bit of a restless person when it comes to photography. I love how versatile the film is and how many looks you can achieve. And you can shoot a single roll, rating it anywhere between 200-800 depending on your needs/desires and still have perfect exposures. Here are some examples at @ 200. At 200, I think it's fairly similar to Portra 400 with fairly bright and almost pastel like colors.
I think the sweet spot is at 400. Warm and quite saturated colors.
At 640, the colors are getting even more saturated and skin tones look delishious.
At 800, it can border on "muddy" depending on the quality of light. But in the right light, it can make for some really deep colors.