I spent most of yesterday designing, milling and building the new circuit board for the Avago ADNS-9500 chip. It took most of today to work through all the software changes required to make it work. It certainly has a much higher DPI capability that is pretty insane. Moving the ball just a little jumps from the edge of one screen all they way over to the edge of the other screen (using two computer monitors). I'm not sure I'll have much use for that in 5670 DPI mode, but it is there should I find a need for it.
From an electrical design standpoint, the ADNS-9500 is very similar to the ADNS-7550. Changes included a new physical package layout, grounding one pin to select between 5V and 3.3V and bumping up the size of one of the capacitors. Other than that, the two chips use exactly the same design.
From a software perspective, I had to make arrangements to download the SROM to the chip every time it boots up. My attempts at this were pretty bad and just crashed my Teensy board. After doing some Google searches, I found a sketch pre-made that worked like a champ. I was able to combine it into my current software to make a working version. I just updated the firmware software to the current version and all is working well. There were a few minor additional changes required to make this chip do all that I had ADNS-7550 doing, but the firmware download was the biggest hurdle. The key ended up being the need to store the SROM image in flash memory on the Teensy instead of the default SRAM since the flash has a much larger capacity.
In addition, I'm using the taller version of the ball support on this new circuit board with a wider set of metal ball support contacts. It is nice and silky smooth. The three metal supports contact the ball just below the equator line. It seems that the further I spread these out, the better the ball movement feels.