I had the 2006 version and my wife got me the 2008 version for Christmas. I used 2006 during my trip to New Mexico and Colorado last summer and it had all the roads we took on it. They were mostly forest service roads.
The new version has lots of cool bells and whistles that the 2006 version didn't have. My wife has an Avon business and I talked her into using 2008 to incorporate her contacts into a "route" on S&T. The program will optimize the route pretty efficiently. She'll deliver product to 30-40 customers at a time and it cuts her fuel usage and delivery time significantly. This point has no real bearing on expedition travel, but in her Sequoia DD, it makes for efficient customer routing anyhow.
In summary, the 2006 version I bought came with the first generation gps. The new version I got for Christmas, has the SIRF III chipset gps, which tracks more satellites and works better in foul weather/around tall obstructions.
I tried using a SIRF III bluetooth gps, the one that the guys took on the Arctic Circle Expedition (I saw it in their thread). It didn't work near as well as the original usb one did. I never determined if the problem was with bluetooth coms or with the gps itself. It seemed to anticipate where the vehicle was travelling instead of reporting actual locations. I ended up mothballing it in favor of the new one that came with 2008.