The distributors finally got in some of the new ST Micro STM32F2 series uControllers and I grabbed a few. I was able to "shoehorn" one into a ver5 board as the pinout is close to compatible with the performance STM32F1 series. Spent a few days rewriting the device drivers and am very impressed with this controller's performance.
I was able to bump up the sample rate to around 276.8KHz for all 12 sensors for a total of ~3.32 million samples per second. Despite this more than doubling of work load, I ended up with around 70% idle time, up from 60% of the STM32F1. Keep in mind that at a 120MHz clock rate, this 70% free cycles represents more than twice as much free number crunching capability than the STM32F1 at 60% idle. I also found that the DMA to be much better with full FIFO available on each DMA channel and an easier to use triple ADC.
The result is a much cleaner interpretation of the sensor data which translates to a smoother and more stable platform.