Same with me, I use now 3 years Copilot, first on the HTC desire and now on the Samsumg Galaxy nexus. It works fine and is stable.
They have now also a function to port serial id by button click to a new mobile. before you had to deactivate your serial on the old phone and to activate on the new one..this was terribale when you are flashing new ROMs all the time...
A year after the last post... The new Copilot Live Premium became quite usable after the update... and after getting a phone with a larger screen - SGN2. The last version 220.127.116.11 can issue speed and camera alerts even without a route! The only problem is lack of mobile cameras POI. This is why I came to this forum... A similar problem is with petrol stations - e.g. one can't display just Shell. I'll try and report back the setup once everything is sorted.
To the earlier query - Copilot uses mobile data in the field only for advanced search. This assumes that all installation, map downloads and other administration is done at home on wifi.