I have a factory unlocked iphone 4 and whilst on iOS 4.1, I became aware that when I installed gyroscope apps, they don't work. When 4.2.1 came out instead of solving the problem, my compass also failed. Both my gyro and compass don't work anymore... 4.3 came out still the same problem.. Now that 4.3.1 came out the accelerometer also failed! Thank god I save my SHSH blobs since I restored back to 4.2.1 Shame on you Apple!!