I had a 2012 670 last year and tried a demo 680, in canola there was pretty much no difference, in heavy wheat it was about 5 acres an hour more and did a better job thrashing, no white heads,a lot cleaner sample. Fuel was a definite increase but when you worked it out per acre it wasn't that terrible. As for lower resale, that's not an issue around here, the 680's at our dealership were sold out a month ago, anyone who usually ordered 670's for the most part went with 680's this year and all the used 680's were spoken for before they even made it back to the dealer. I wanted one this year but couldn't get one so I traded on a 690