The cursor drifts off the screen.

Generally speaking you should not have problems with the cursor drifting since the mouse was calibrated prior to shipping. Turn the mouse off then on, to reset the device. Double click the Gyro activation button (this will keep the gyro on).
Set the mouse on a steady surface (table top). Since this is a mouse you will have to set it on its side or with the front of the mouse hanging over the edge, otherwise the desktop sensor will automatically activate and stop the Gyro function.
The cursor will start to drift but should stop within 7 to 10 seconds as the Gyro re calibrates.

My wireless network is causing interference. Can this be corrected?

The Gyration 2.4GHz product uses a technique called interference avoidance so it will automatically channel away from wireless networks, Bluetooth devices etc. The problem with network interference generally is caused by the wireless router or access point being set up to broadcast over the entire 2.4GHz band. There should be set up options in the router or access point to set the broadcast bandwidth to something other than all 800 channels available in the 2.4GHz band. Once the SSID is changed the problem should go away (preferred non-overlapping channels are 1, 6, and 11).

The Cursor movement is choppy or erratic.

Move the USB receiver to a different USB port (front of system vs. back) or try a short USB extension cable to move the USB receiver.
There could be radio interference. Move the receiver away from other electronic devises (e.g. monitor, speakers, radio, etc.).