Are all features of Gyroscope supported by all mobile Android or iOS devices with gyroscopes? http://unity3d.com/support/documentation/ScriptReference/Gyroscope.html
No, only for iOS.
Galaxy Tab 10.1 is giving me Gyroscope output so yes it is supported in Unity 3.5
It is, but it seems that if you use Input.gyro.enabled it will by default return false unless you set it to true - if gyro is not available on the device it will continue returning false even if you try set it to true.