Rod1,
Flying in the SE I generally find I can get something out of ATC, if I ask. Could it be a lot better? - of course, but ATC can also provide a lot better information with less work if they are calling relevant mode c traffic vs various mode A and non-transponding possible targets.
For people who fly in the truely open FIR off grass fields no where near controlled airspace then the value of a transponder is low - but I would have thought these people are not going to have invested very much in avionics (1 radio and a hand held GPS maybe) given that they are not going to be going very far - and my arguement for installing Mode C isn't directed at this type of flying. Once you plan on going somewhere you are going to be mixing with people who are getting a service and are carrying technology to detect you (even if it is very basic with just a range, relative altitude and maybe rough bearing)