Would i be correct in thinking that the hardware hasn't changed at all since the first version and that realy it is only the software that has changed?
From what I've seen here from the AirNav contributors, there have been few changes, if any, to the hardware. The latest Radarboxes come with firmware that has a different version number, but is also claimed to be effectively unchanged. The driver version number has changed at least once, there may be another update to that as there is a later version on the FTDI site, it would be part of a new software release I assume.
There have been about 8 software releases, the latest from August 2008, and it was mentioned that the 2.1 release is expected late this month.