Seems like that in this part of the country, the D7 series fell in popularity when they got too big to be hauled on a 5 axle rig when fitted with a winch or a ripper or a heavy V shear blade or rake blade. If you've got to upgrade to a 3 axle lowboy, you might as well get a D8K or later and have a real workhorse. I'm not saying that the D7 tractors don't have their place, but my D6R will outwork my D7E, using less fuel and with the 7 roller XL configuration it produces far superior work. I suppose it all depends on your application, but the 6R and 6T sure do seem to be the right size for us small dirt and timber contractors with multiple job profiles. The big timber contractors use D8s, and the the big highway and civil contractors use a lot of D5Ks and D6Ks for dirt work.
Bullcat, have you had a chance to use your d7r yet? I put the sweeps on mine and changed the air fuel control device today and played with it for a half hour. It was in a pile of sticky muck that my old d7e had it's hands full in. I was able to roll dirt in second gear, the old one would push dirt in second gear but would only roll it in first. I'm thinking I'm going to like the cab. My helper wanted to ride in it.
