Provia 100F is also my standard color film. It pushes well with a slight (and I do mean slight) shift toward red in skin tones, and blue skies shift ever so slightly towards purple in the evenings. When I do this I expose at 320 and ask the lab for a 2 stop push.
How about the grain when you push Provia? Any noticeable change?
I'm wondering as well, is there any advantage to pushing 100F as opposed to just using Provia 400X?