@tai : "They also arrange the photosites horizontally, rather than diagonally like Nikon" its the other way around. ie the Fujifilm sensor is arranged diagonally. (Yeah I know its a typo..)
I have an S5pro. And it is/was a bit soft when it outputs the 12MP jpegs. It performed like an 8-9 MP camera in terms of details captured. Performance wise in terms of acquiring focus its better than my d70 but not as good as the d200. HOWEVER there has been an Firmware update early this year and the focusing has been improved by a lot. Also the Jpg output is much sharper. not quite 12MP but maybe 10+ MP. Its almost like a new camera!. I was about to get a D300 when the firmware update came out. I was so pleased with the update I have put of buying a new camera for a while.
Another thing said about the S5pro performance is that its FPS is only about 2 FPS. But you don't get much more from a D300(2.5 FPS) if you use the high quality 14 bit capture mode instead of the 12 bit.
The JPG output from the S5pro is really amazing. Even on the JPG you can recover much more highlight detail than from a D200. ie the DR on JPG of the S5pro is almost like RAW! ( Check out Ken Rockwell's review on the S5pro which compares the S5pro against the D200.) The DR of the JPG from the s5pro is 11.5 ev while most cameras RAW DR is 7-10 ev. The DR of the S5pro RAW file is almost 14EV !!! Nope there is no other camera that is even close to the S5pro DR at ISO 800 or less. Its no wonder that Wedding photographers use the Fujifilm SLR!
I love myS5pro for Nature shots as it tames the harsh lights.
This picture taken around mid day! see no harsh highlights !! and lots of nice details in the black as well as the white feathers.
New Holland Honey eater

PS: And I have not even mentioned the Colours!