I'm having a lot of orientation issues as well. Sometimes, when I take the phone out of my pocket, the orientation will be upside down...as if it flipped while in my pocket, but that doesn't make much sense because my screen was never on while in my pocket (that I'm aware of anyway). Other times, the phone gets stuck in landscape mode. If I flip the phone 180 degrees it wont rotate. If I rotate it 90 degrees into portrait mode, that works fine. Also, I've had issues with rotating from portrait to landscape and the keyboard not working. Sometimes, the whole screen is frozen too until I switch to portrait and back several times.
This and the WIFI issues are the only problems I've had so far with iOS 8. Otherwise, it's been great!