I wish there was more detailed technical information on the page. I've been trying to figure out how precise the timer is, or at what frequency you can read from the pins. The answer seems to be provided on pages 112+ in the datasheet of the micro controller, but in a not very easy to understand format for the aspiring programmer without EE knowledge.
If I recall correctly, at least some of the STM32F4 timers can be clocked at the same frequency as the system clock, so 168MHz maximum.
The GPIOs can be configured with a maximum 100MHz clock, though your software likely cannot read the registers that quickly if it is going to do much else.
EDIT: The reference manual actually contains a lot of the peripheral details, with the datasheet containing the chip specific details, like clock speed and which peripherals are present.
http://www.st.com/web/catalog/mmc/FM141/SC1169/SS1577/LN1035...