I have tested the compass feature on 655t with mixed results.
Firstly, the manual does not specify the reference point for compass, I assume you have to hold the device horizontally and use the direction of antennas as reference point - since this most important fact is not specified in the manual it is already a big red flag about technical sloppiness.
Secondly, the compass is not accurate. I was comparing it to a traditional magnetic compass. The manual says about calibration but I am wondering why would the calibration be required. Did anybody tried to calibrate and achieved legitimate practical compass on 655t, or its compass is just a gimmick feature to be ignored.