I think that the D300 is an excellent camera, as are the 5D, 1Ds Mk3, D3 etc - for what they were designed to do. I think the points coming out of this discussion suggest that both have positives and negatives and it is the sweeping statements of FF good, DX bad (or vice versa) that are misleading.
And we may now be now far from the topic of speculation of specific models yet to come...
With that, I think what Adams wrote quite a time ago still resonates simularily to the process of FX/DX today.
"If we fail to comprehend the medium, or relinquish our control to automation of one kind or the other, we allow the system to dictate results instead of controlling them to our own purposes. The term automation is taken here in its broadest sense, to include not only automatic cameras, but any process we carry out automatically, including mindless adherence to manufacturers’ in such matters as in film speed rating or processing of film. All such ratings are based on an average of diverse conditions, and can be expected to give only adequate results under “average” circumstances, they seldom yield optimum results, and then only by chance. If our standards are higher than average, we must control the process and use it creatively.
Ideally, a photographer develops a personal style and works with a camera format that compliments it. But a photographer who uses several different camera types will often find that his very perception changes when he is carrying a large camera instead of a small one, and visa versa. Knowing the characteristics of each camera type can helps us appreciate its advantages, while coping successful with its drawbacks."
And before you say, "Duh". I just meant to show that I agree with what Alex is saying on sweeping statements of good or bad and not my intent. Only that the D3 series now offers us a way to almost have two cameras in one for the advantages of different optics and being able to match those up more closely to our desired effect.
Just as the D10 or Dxx will probably allow us to have video and slr capabilty in one camera some day, but it wont be good versus bad then either. I'll go be quiet now.