As much as I love my S90, if the GF1 isn't too big for you to carry as much as you would the Canon, the 4:3 sensor and MUCH broader lens options would be the deciding factor for me in favour of the GF1. If the GF1 is too large for you and you will end up leaving it home more often then not, it doesn't matter how much better a camera it is, the S90 would be the better choice.
My D700 is by far the best camera I've ever owned, but I bought an S90 because the D700 is just too damned big to carry for anything but that which I'm being paid to shoot.