So as a test, a colleague and I took it with us for a short drive upto Adyar (just about 3 km from the institute) and back. It dutifully recorded the car speed and to our astonishment, almost all the roads and landmarks (including obscure details like Thiruvanmiyur HIG flats, 'going under the Adyar flyover'). It produced useful information like nearby restaurants (Pizza Hut, Adyar Ananda Bhavan....), and help areas like VHS (Voluntary Health Services) 300 metres down the road from where we were, and a bunch of other clinics we had never heard of. The wealth of detail available is truly impressive -- both regarding roads, as well as nearby landmarks, shops, restaurants and hospitals. Clearly someone, or some people have been at work, entering this information into the google database. Along the way you can even SMS your position to someone who might be waiting for you (it sends a http link to a google map) or you can email it (it uses gmail preferably or some other push mail interface through your GPRS connection).
Overall a very satisfying experience. Perhaps this is all standard for GPS assisted navigation, but since this was my first, I am allowed to get a thrill our of it :-).