Come on we've heard this record before, someone screws up and blames the GPS. Last time I saw this someone was driving too fast to actually follow the directions.. and still blamed the GPS.
And once again the masses expect DGPS accuracy on a stand alone gadget.
GPS track depends on time of day? Not a surprise. Anyone who knew how GPS actually works could tell you about how the environment can introduce offset errors.
If people actually spent a morning understanding the basic theory of their toys they might actually get the most out of them. In britain at the moment you have to have at least a basic understanding of a car before you're licensed to drive one. You have to understand road surfaces, conditions, visibilities, laws, engine characteristics, symetry... How many of the great unwashed understand their PC hardware or operating system in the same depth?
I'm not expecting anyone to be able to build a GPS unit from off the shelf parts, but if you expect anything to work by infalible magic you will be disapointed.
Until black-box models are banned for being racially demeaning, you have no excuse for ignoring their validity conditions.