I used the Fuji S1 Pro at work when I worked for a photography studio company. They let me take the camera off location, which was really cool because at the time, this was a higher end digital camera. It produced a good image at about 4MP, if I remember right. The only real thing that I could complain about with this camera was the horrible battery life. It quickly sucked batteries dry, and it required both AA and Nickel batteries. I'd have to change batteries every 100 pictures or so. It seemed to get dirty often, and eventually it started to have dead pixels meaning that every picture had little black dots where the camera wouldn't render the proper color.
I got around the dead pixel problem by using Photoshop's clone tool, but this became really annoying to have to deal with on every picture that I wanted to keep.
The photo studio that I used to work for now uses the S5 Pro and they love it. They said the battery life is much better, and it produces really good pictures. In the professional arena, it's not that expensive. This is a good thing because they tended to break cameras a lot, so replacing a $1700 camera is easier to stomach than a $5000 camera. The S5 is a camera that I've had my eye on for a while now and may eventually purchase.
To get to the point, the S1 Pro is ancient history. The S5 is a great camera that is being used by professional portrait studios and is worth taking a look at.