I have always thought that the D300, altough excellent, is too large and heavy for not being FF, the 7D has almost excatly the same size and weight.
The size of the D300 comes from having a metal chassis, additional controls on the outside of the body, a full size viewfinder and more ruggedness and seals than the D90. If you want a smaller body, go buy the D90. I personally want a DX body and don't want to give up any of the things that the D300 brings over the D90.
Why do you think that because it's DX, it should be tiny or because it's a good sized body, it should be FX. That's ridiculous. DX vs. FX is only one thing that contributes to the size constraints of the body - there are many other factors that have nothing to do with the sensor size.
Some of us want as full a featured DX body as we can get and in today's Nikon lineup, that's the D300s body. I personally don't think Nikon should stop filling that spot in the market.
If you want to argue for more features in the D90 body size, then that is what is rumored to be the D95 and you can focus on that part of the discussion.
If you want to argue for a smaller FX version of the D700, then make a separate argument for that new product, but neither of those arguments have anything to do with the D300 because it serves a very different market need than the D700 or a smaller D700.