I have been unable to get the DHT22 temp/humid sensor to work at 8mhz on a homemade board... I know it works with my UNO, I know it works with my home made board at 16mhz... But I could not get it to work using the internal 8mhz clock or an external 8mhz crystal on the homebrewuino.
Again, 16mhz Uno and home brew works as intended. Without changing the wiring, I burn a 8mhz bootloader on the home brew and the sensor always reads 0% humidity, 0 degree temp without a "failed read" error. If I pull the signal pin, then I get a failed read error. So the sensor is getting sending information, just not the correct information.
I peeked into the library (adafruit DHT lib) and didn't see anything that would change performance based on clock speed... but then again, I'm a noob....