Summary: I upgraded from a Zumo 550 and have used the inferior Tom Tom variants. The locking screw is no longer there but this unit is a more conventional size/shape, so can be stowed easier in the supplied and robust case. The functions have been finessed and the display is sublime. It loads the maps, acquires the satellites and calculates routes faster than before. The lifetime map updates is a bonus.
Summary: I purchased this for the dual roles of my car and motorbike. I have tried it on bth and found it to be very clear to understand. I spent a little while intentionally going the wrong way and the 660 very quickly recalculated instead of trying to nag me to turn around like some sat-navs do. It is well constructed and works well with my Interphone bluetooth comms set and Galaxy SII smartphone.