I have used a Colorpack II with some FP-100B.
It works just fine. At first I thought I would need to adjust the magic eye but it turns out the 1/4 stop difference between the Fuji and Polaroid is barely noticeable.
Just a few things to be careful with. If your model has the spreader bars (like mine), you have to pull very straight and fairly hard to extract the film. The only time I had problems is when I used the pull strap on the camera like they said on the instructions! It's easy to pull the film crooked and the leader on the Fuji film will rip if not handled properly. But apart from that, if you're careful to always eject the film straight, there's no problem there.
Also, when you press the button, you have to leave your finger on it until the second click in order to get the correct exposure. Just regular Polaroid stuff.
Results... I don't know where I put the prints but I remember they were a tiny bit softer than my 315 folder but still quite nice.
