I also installed a DHT22 two days ago and it seems to work fine. Some informations about my case :
* My banana pi is mostly idle so running at 600Mhz
* I used a 5.1kΩ as a pull-up
* I used 40cm cables to put the DHT22 as far as possible to any heat source
* I'm also using Bananian with lol_dht22
I check with a oregon scientific temperature sensor and it seems mostly good for the temperature (not so good for humidity), I also opened a window and I saw the temperature and humidity drop.
I'll receive a DS18B20 in a few day so I'll be able to compare.