Looking at the specs, I think that it will be unfair to pitch it against the D300.
The D300 will still outclass it in nearly every way
Until Pentax change their autofocus to be quicker, sharper, more accurate AND include predictive autofocus there will be no comparison.
Also, why does the frame rate not increase when adding the battery grip?
The only thing stopping a body change is the money - still now the D300 is out of production, maybe the prices will slip a bit and I can get one next year.