It seems the readings can be pretty erratic, jumping from near zero to 0.4 or 0.5 even when the device is completely still.

How do you all deal with this? I tried taking the average of the last 5 readings which seems to help a little but it's still kind of jumpy.

Have a look. This is sitting completely flat on the desk:

X: -0.021 Y: -0.011 Z: -0.987
X: 0.421 Y: -0.014 Z: -0.986
X: 0.421 Y: -0.014 Z: -0.987
X: -0.018 Y: -0.016 Z: -0.986
X: -0.022 Y: -0.014 Z: -0.986
X: 0.423 Y: -0.013 Z: -0.987
X: 0.42 Y: -0.015 Z: -0.987
X: 0.417 Y: -0.013 Z: -0.988
X: 0.419 Y: -0.012 Z: -0.984
X: -0.015 Y: -0.011 Z: -0.984
X: -0.02 Y: -0.013 Z: -0.987
X: -0.017 Y: -0.014 Z: -0.987
X: 0.423 Y: -0.014 Z: -0.988
X: -0.019 Y: -0.012 Z: -0.986
X: -0.027 Y: -0.013 Z: -0.988
X: 0.421 Y: -0.013 Z: -0.99
X: 0.423 Y: -0.017 Z: -0.988
X: 0.421 Y: -0.016 Z: -0.988
X: 0.423 Y: -0.011 Z: -0.987
X: 0.42 Y: -0.008 Z: -0.987
X: -0.021 Y: -0.013 Z: -0.986
X: -0.018 Y: -0.014 Z: -0.99
X: -0.022 Y: -0.011 Z: -0.99
X: 0.42 Y: -0.013 Z: -0.984
X: 0.423 Y: -0.012 Z: -0.988
X: -0.023 Y: -0.014 Z: -0.984
X: 0.421 Y: -0.016 Z: -0.985
X: 0.417 Y: -0.015 Z: -0.985